Mulch Calculator
Work out exactly how much mulch a job needs — for one bed or for a whole yard of beds, borders and tree rings — in cubic yards, cubic feet, litres or bags, with the mulch already on the ground taken off the top and the bagged and bulk purchase costed side by side.
Net volume, planning allowance, required volume and purchased volume are four different numbers here — and the allowance starts at 0%, because settling is your decision to make, not a percentage this page adds behind your back.
Verified Additional depth ≥ 0, required ≥ net, purchased ≥ required, overage ≥ 0 and every package quantity is a whole number.
- Net mulch volume
- 1.85 yd³area × additional depth — pure geometry
- Planning allowance (0%)
- 0 yd³a choice, not a requirement — the default is 0%
- Required volume
- 1.85 yd³net + allowance
- Exact bag-equivalents
- 25 bagsthe mathematical figure — not purchasable
- Whole bags to buy
- 25rounded up: bags do not split
- Purchased volume (bags)
- 1.85 yd³what you leave the shop with
- Package rounding overage
- 0 yd³bought because bags are whole units
- Bulk supplier order
- 1.85 yd³no supplier increment or minimum entered — this is the required volume itself
- Bulk purchase overage
- 0 yd³supplier rounding, not waste
Project breakdown
| Area | Shape | Area size | Target depth | Existing | Added depth | Volume |
|---|---|---|---|---|---|---|
| Bed 1 | Rectangle / square | 200 ft² | 3 in | 0 in | 3 in | 1.85 yd³ |
| Project total | 1 area(s) | 200 ft² | — | — | 3 in mean | 1.85 yd³ |
Bags or bulk
| Bagged | Bulk | |
|---|---|---|
| Required volume | 1.85 yd³ | 1.85 yd³ |
| Quantity to order | 25 whole bags (25 exact) | 1.85 yd³ |
| Purchased volume | 1.85 yd³ | 1.85 yd³ |
| Purchase overage | 0 yd³ | 0 yd³ |
| Cost | add a bag price | add a bulk price |
Add a bag price and a bulk price to compare the two ways of buying.
Break-even: Enter the price of one bag to find the break-even.
See the math
Every headline number above can be rebuilt from these rows with a pencil.
- Mode
- Quick estimate
- Canonical units
- Lengths and depths → metres · areas → square metres · volumes → cubic metres. Every input is converted once; display units never feed another conversion.
- Original inputs
- Length 20 ft · Width 10 ft · target depth 3 in · existing mulch 0
- Normalized units
- Length = 6.096 m · Width = 3.048 m · target 0.0762 m · existing 0 m
- Area formula
A = L × W- Area substitution
- 6.096 m × 3.048 m = 18.5806 m²
- Top-up depth
- additional = max(target − existing, 0) = 0.0762 m (3 in)
- Volume formula
V = A × d- Volume substitution
- 18.5806 m² × 0.0762 m = 1.41584 m³
- Area net volume
- 50 ft³ · 1.8518518519 yd³ · 1.4158423296 m³
- Material (context only)
- Shredded bark — the material never changes the geometric volume.
- Area source
- Measured dimensions
- Net mulch volume (unrounded)
- 50 ft³ · 1.8518518519 yd³ · 1.4158423296 m³
- US shortcut check
- cubic yards = square feet × depth in inches ÷ 324 → 200 × 3 ÷ 324 = 1.8518518519 yd³
- Planning allowance
- 0% → 0 yd³ (none applied — this calculator never adds one for you)
- Required volume (unrounded)
- 50 ft³ · 1.8518518519 yd³ · 1.4158423296 m³
- Displayed result
- You need 1.85 yd³
- Package rounding
- exact bag-equivalents 25 → ⌈ ⌉ → 25 whole bags of 2 ft³ = 50 ft³ purchased, overage 0 ft³
- Supplier rounding
- No supplier increment or minimum entered, so the bulk order equals the required volume exactly.
- Rounding policy
- Nothing intermediate is rounded. Whole bags and supplier increments are rounded up mathematically; everything else is rounded for display only, with a documented 1e-9 relative tolerance so 26 ft³ in 2 ft³ bags is 13 bags and never 14.
- Density / weight
- No volume is converted to a weight anywhere on this page: that needs a bulk density, which is a property of your specific product.
- Verification
- Verified — Additional depth ≥ 0, required ≥ net, purchased ≥ required, overage ≥ 0 and every package quantity is a whole number.
- Engine
- mulch-engine v1.0.0 · state v1 · receipt 1.0.0
How much mulch do I need? The short answer
Mulch volume = area × depth. That is the whole calculation. Everything else on this page exists because of what happens either side of it: the depth you are adding is not always the depth you want, and the volume you have to buy is not the volume the geometry needs.
In US units the two conversions collapse into one constant:
cubic yards = square feet × depth in inches ÷ 324
The 324 is not a magic number. One cubic yard is 27 cubic feet, and one inch of depth is 1/12 of a foot, so a cubic yard spread one inch deep covers 27 ÷ (1/12) = 324 square feet. Divide 324 by the depth in inches and you have the coverage for that depth: 162 ft² at 2 in, 108 ft² at 3 in, 81 ft² at 4 in. In metric there is no constant to remember, because a depth in metres times an area in square metres is already cubic metres.
The formulas this page uses
area = shape formula (A = L × W, A = πr², A = π(R² − r²), A = ½bh, A = ((a+b)/2) × h, outer − inner)
additional depth = max(target depth − existing depth, 0)
net volume = area × additional depth
required volume = net volume × (1 + allowance ÷ 100)
exact bag-equivalents = required volume ÷ bag volume
whole bags = ⌈required volume ÷ bag volume⌉
supplier order = ⌈required ÷ increment⌉ × increment, then raised to the minimum
coverage area = available volume ÷ depth
Every one of those is implemented exactly once, in mulch-engine v1.0.0, and every table further down this page is generated by calling it. There is no second copy of the arithmetic in the prose, which is why the tables cannot drift away from the calculator.
A worked example you can check by hand
A bed 20 ft × 10 ft, mulched 3 in deep, with nothing on it yet:
- Area: 20 × 10 = 200 ft²
- Depth in feet: 3 ÷ 12 = 0.25 ft
- Volume: 200 × 0.25 = 50 ft³
- Cubic yards: 50 ÷ 27 = 1.8518518519 yd³
- Or by the shortcut: 200 × 3 ÷ 324 = the same 1.8518518519 yd³
- In 2 ft³ bags: 50 ÷ 2 = 25 bags, exactly — no rounding needed this time
That is the calculation the tool is showing above right now, produced by the same engine: the numbers in this paragraph are read out of the result rather than typed alongside it.
How deep should mulch be? What the sources actually say
There is no universally correct depth, and this calculator will not pretend otherwise by pre-filling one as if it were a fact. What follows is what named university Extension publications say, with the context each of them is answering. The published figures in this dataset span 1–4 inches across 5 claims from 3 institutions, and they do not all agree — the coarse-versus-fine distinction and the plant matter more than any single number.
| Context | Depth | What the source says | Source |
|---|---|---|---|
| Coarse organic mulch around landscape trees and shrubs, on well-drained soil. | 2–4 in | Apply a 2- to 4-inch layer of organic mulch and no more, using less where the soil is poorly drained. | Penn State Extension — Mulching Landscape TreesRetrieved 2026-08-17 · source revision 2018-04-12 |
| Finely textured mulches (such as fine, well-decomposed material) around landscape trees. | 1–2 in | Use only 1 to 2 inches of a finely textured mulch, because fine material lets less oxygen reach the root zone. | Penn State Extension — Mulching Landscape TreesRetrieved 2026-08-17 · source revision 2018-04-12 |
| Organic mulch in home landscape beds, generally. | no more than 3 in | Organic mulches should not exceed three inches in depth. | University of Maryland Extension — Excess Mulch ProblemsRetrieved 2026-08-17 · source revision 2023-03-14 |
| Shallow-rooted woody plants (boxwood is the example given). | no more than 1 in | Shallow-rooted plants such as boxwood should not have more than one inch of mulch over their roots. | University of Maryland Extension — Excess Mulch ProblemsRetrieved 2026-08-17 · source revision 2023-03-14 |
| General garden and landscape mulching for soil and garden health. | 2–4 in | Apply mulch about 2 to 4 inches deep to balance weed suppression against soil aeration. | University of Minnesota Extension — Mulching for soil and garden healthRetrieved 2026-08-17 · source revision 2026 |
These are records of published guidance, retrieved on the dates shown; Extension pages are revised, so follow the links for the current wording in full context. The calculator itself contains none of these numbers: remove this dataset and the arithmetic is unchanged.
Already have mulch? Calculate the top-up, not the full layer
This is the single most common mulch-estimating error, and it is expensive in both directions: order a full layer on top of an existing one and you buy roughly half again as much mulch as the bed can take, then pile it too deep, which is exactly what the sources above warn against.
top-up depth = target depth − current depth
Worked through: a bed of 100 ft² with a 3 in target and 1 in already down needs 2 in of new mulch, not 3. That is 16.6666667 ft³ — 0.61728395 cubic yards, or 9 whole bags of 2 ft³. Calculating the full 3 in would have called for 25 ft³ instead.
And if the bed already has as much mulch as you want — or more — the honest answer for that bed is zero. The calculator returns zero and says why, rather than recommending a token amount to keep the number looking useful.
Bags or bulk?
The trade is simple to state and impossible to answer in the abstract: bags cost more per unit volume but you buy exactly the number you need and carry them yourself; bulk is cheaper per yard but adds a delivery fee, often a minimum order, and usually an increment you cannot go below. Which wins depends entirely on your prices and your supplier's terms, which is why this page asks for them instead of quoting an average.
Two details make most bags-versus-bulk comparisons wrong:
- Both sides are step functions. You cannot buy 12.5 bags, and a yard that sells in half-yard scoops will not deliver 1.85 yd³ — it will deliver 2.0. Costing the theoretical requirement instead of the actual purchase understates both sides, and it understates them by different amounts, which can flip the answer.
- The break-even is not a division. Because both curves step, dividing the bag price by the bulk price names a quantity nobody can buy. This page finds the crossing by walking every purchasable quantity — every whole bag, every supplier increment, with the minimum order and the fixed fees applied — and reports the first requirement at which bulk stops costing more and stays that way. When there is no such point in the searchable range, it says so instead of inventing one.
Irregular beds and several beds at once
Real gardens are not one rectangle. Two things fix that. For an irregular bed, break it into pieces you can genuinely measure — rectangles, triangles, circles — and add them; the calculator has a mode for exactly that, and each piece stays visible in the receipt. For an outline you cannot reach with a tape, measure it on a map: the area comes from the geographic coordinates of the points you place, computed by the same geodesic engine the Area Calculator uses, and it arrives in the project as an ordinary area with its source recorded.
For several beds, use Project Builder. Each area keeps its own shape, units, target depth, existing layer and quantity, and can be excluded without being deleted while you price alternatives. The project total is the sum of the included areas at full precision — and that matters more than it sounds: rounding each bed up to whole bags and then adding them is how a five-bed job quietly gains a yard of mulch that no bed asked for.
Tree rings: the ring, not the circle
A tree ring is an annulus, not a disc, because you are deliberately leaving the ground next to the trunk bare:
A = π(R² − r²)
With a 10 ft outer diameter and a 2 ft bare centre that is π(5² − 1²) = 75.40 ft², against 78.54 ft² for the full circle. The calculator excludes that inner circle physically, from the measurement you give it — it does not apply a clearance of its own, because the published clearances differ:
- Keep all mulch away from the trunk and let the root flare — where the trunk meets the soil — remain visible. — Penn State Extension, Mulching Landscape Trees, retrieved 2026-08-17. The same page suggests pulling mulch roughly 3 to 5 inches back from young trees and 8 to 10 inches from mature trees, and states that "volcano" mulching is never recommended.
- Keep mulch about three inches away from the base of the trunk so the bark is not kept wet. — University of Maryland Extension, Excess Mulch Problems, retrieved 2026-08-17.
- Leave a mulch-free ring around the trunk — the page suggests about six inches. — University of Minnesota Extension, Mulching for soil and garden health, retrieved 2026-08-17. Three institutions, three different clearances — which is precisely why this calculator does not apply one for you.
What the sources agree on is the principle rather than the number: mulch should not be piled against the trunk, and the root flare should stay visible. The geometry and the horticulture are kept apart here on purpose — the calculator measures the ring you describe, and the guidance above tells you what the sources say about describing it.
How much area does one cubic yard of mulch cover?
| Depth | One cubic yard covers | …in metric | One 2 ft³ bag covers |
|---|---|---|---|
| 1 in | 324 ft² | 30.1 m² | 24 ft² |
| 2 in | 162 ft² | 15.1 m² | 12 ft² |
| 3 in | 108 ft² | 10 m² | 8 ft² |
| 4 in | 81 ft² | 7.5 m² | 6 ft² |
How many bags of mulch in a cubic yard?
| Bag size | Exact bag-equivalents in 1 yd³ | Whole bags to equal or exceed 1 yd³ | Volume purchased | Overage |
|---|---|---|---|---|
| 1 ft³ bag | 27 | 27 | 27 ft³ | 0 ft³ |
| 1.5 ft³ bag | 18 | 18 | 27 ft³ | 0 ft³ |
| 2 ft³ bag | 13.5 | 14 | 28 ft³ | 1 ft³ |
| 3 ft³ bag | 9 | 9 | 27 ft³ | 0 ft³ |
How much mulch for 100, 250, 500 and 1,000 square feet?
| Area | 1 in | 2 in | 3 in | 4 in |
|---|---|---|---|---|
| 100 ft² | 0.31 yd³5 bags of 2 ft³ | 0.62 yd³9 bags of 2 ft³ | 0.93 yd³13 bags of 2 ft³ | 1.23 yd³17 bags of 2 ft³ |
| 250 ft² | 0.77 yd³11 bags of 2 ft³ | 1.54 yd³21 bags of 2 ft³ | 2.31 yd³32 bags of 2 ft³ | 3.09 yd³42 bags of 2 ft³ |
| 500 ft² | 1.54 yd³21 bags of 2 ft³ | 3.09 yd³42 bags of 2 ft³ | 4.63 yd³63 bags of 2 ft³ | 6.17 yd³84 bags of 2 ft³ |
| 1,000 ft² | 3.09 yd³42 bags of 2 ft³ | 6.17 yd³84 bags of 2 ft³ | 9.26 yd³125 bags of 2 ft³ | 12.35 yd³167 bags of 2 ft³ |
Common mistakes
- Using inches as if they were feet. A 3 in depth is 0.25 ft. Typing 3 into a field expecting feet gives twelve times too much mulch.
- Stopping at square footage. Mulch is sold by volume, not by area. A square-foot figure with no depth attached cannot be ordered from.
- Rounding every bed before adding them. Round each of five beds up to whole bags and the project gains material nobody measured. Sum first, round once.
- Calculating the full depth on a bed that already has mulch. Only the difference is bought — and topping an existing layer up to the full target depth twice over is how mulch ends up too deep.
- Treating fractional bags as purchasable. 12.5 bag-equivalents means 13 bags. The exact figure is the maths; the whole number is the purchase.
- Assuming every bag is 2 ft³. Bag sizes vary by brand, product and country. Use the volume printed on yours.
- Treating an automatic 10% as a requirement. A settling allowance is a decision, not a measurement. Here it defaults to 0% and is always shown on its own line.
- Piling mulch against the trunk. Every source cited on this page says not to, and none of them describes it as a matter of taste.
Methodology & verification
Three modes run on one dedicated engine stack (mulch-engine v1.0.0). Every dimension is parsed once and converted to canonical SI — lengths and depths to metres, areas to square metres, volumes to cubic metres — before any geometry runs, so mixing feet, inches, yards, centimetres and metres can never apply a conversion factor twice, and a display unit is never the input of another conversion. Eight bed geometries (rectangle, circle, tree ring/annulus, triangle, trapezoid, rectangular border, known area and a sum of measured pieces) produce an area; the volume chain is then the same for all of them: additional depth = max(target depth − existing depth, 0), and V = area × additional depth. A bed that already has as much mulch as you want returns zero, not a token amount, because calculating a full layer over an existing one is the most common mulch-estimating error. Four quantities are kept separate throughout and never merged into the word "waste": net mulch volume (pure geometry), planning allowance (a deliberate choice that defaults to 0% and is never added automatically), required volume, and purchased volume once whole bags or a supplier increment and minimum have been applied. Intermediate values are never rounded; rounding happens only for display and at the two genuinely discrete steps — whole bags and the supplier order — each with a documented 1e-9 relative tolerance so a requirement of 26 ft³ in 2 ft³ bags is 13 bags and never 14. No price, delivery fee, bulk density, truck capacity, bag size or supplier minimum is stored anywhere: every one of those is an input, because they vary by product, yard, region and season. No volume is converted to a weight, because that needs a density this calculator will not invent. Depth guidance is a separate, source-backed dataset carrying the claim, its context, the depth range, the institution, the document title, the URL and the retrieval date for every entry — the calculator runs identically with that dataset removed. Each result ships a calculation receipt with the original inputs, the normalized units, the formula, the substitution, the unrounded and displayed results, the allowance, the package rounding, the supplier rounding, the engine version and a fail-closed verification: if an invariant breaks, the page shows a structured error instead of a plausible-looking number.
- Canonical units: lengths and depths in metres, areas in square metres, volumes in cubic metres, from the shared unit registry's exact international factors (1 in = 0.0254 m, 1 ft = 0.3048 m, 1 yd = 0.9144 m). The cubic factors are derived from those, so 1 yd³ = 0.764554857984 m³ exactly and ft² × in ÷ 324 is exact rather than approximate.
- Formulas: the eight area formulas, V = A × d, the allowance, the bag rounding and the supplier rounding each exist exactly once and are listed above.
- Top-up: additional depth = max(target − existing, 0). An area at or above target contributes exactly zero and is reported as such.
- Planning allowance: a separate quantity, defaulting to 0%, never applied silently and never labelled "waste".
- Package rounding: whole bags only, ⌈required ÷ bag volume⌉, with the exact bag-equivalent always shown beside it.
- Supplier rounding: the increment first, the minimum order second, both from your supplier's terms and neither assumed.
- Rounding policy: nothing intermediate is rounded. Display rounding never feeds another calculation, and the two discrete steps use a documented 1e-9 relative tolerance so a requirement of 26 ft³ in 2 ft³ bags is 13 bags and never 14.
- No hidden prices: every price, delivery fee and fixed fee is an input. No average, no benchmark, no stored figure of any kind.
- No hidden densities: no volume is converted to a weight anywhere, because that needs the bulk density of a specific product.
- Invariants: additional depth ≥ 0, required ≥ net, purchased ≥ required, overage ≥ 0 and an integer bag count are asserted on every result, and the project total is independently recomputed from its areas. A violation produces a structured error, never a plausible-looking number.
- Depth guidance: a separate dataset, 5 depth claims and 3 trunk-clearance claims from 3 university Extension publications, each with its context, source, URL and retrieval date. Validation status at build time: passed.
Assumptions
- Mulch is assumed to be spread at a uniform depth across the area you entered; real beds vary.
- Every dimension is normalized to metres before any geometry runs, and the display unit never changes the physical result.
- The top-up depth is the target depth minus the depth already there, floored at zero — an area at or above target needs nothing.
- No settling, compaction or waste percentage is added unless you deliberately choose a planning allowance; the default is 0%.
- Bag volumes, bag prices, bulk prices, supplier increments, minimum orders and delivery fees are the figures you supply. None is stored, assumed or averaged.
- Whole bags and whole supplier increments are rounded up: you cannot buy 0.4 of a bag, and a yard that sells in half yards will not deliver 1.85.
- Material type is context only. Choosing cedar instead of wood chips does not change the geometric volume of the bed.
- Volumes are never converted to weights, because that needs the bulk density of your specific product.
Sources
- Mulching Landscape Trees — Penn State Extension, The Pennsylvania State University. David R. Jackson, Former Extension Educator, Renewable Natural Resources. Source revision 2018-04-12; retrieved 2026-08-17.
- Excess Mulch Problems — University of Maryland Extension, University of Maryland. University of Maryland Extension, Home & Garden Information Center. Source revision 2023-03-14; retrieved 2026-08-17.
- Mulching for soil and garden health — University of Minnesota Extension, University of Minnesota. Robin Trott, Extension educator. Source revision 2026; retrieved 2026-08-17.
Author: Ugo Candido · Last updated: · Calculation engine: mulch-engine v1.0.0 · External review status: No independent third-party review of the calculator. The author is responsible for the methodology; correctness is enforced by the engine's golden reference vectors, unit-equivalence and invariant suites, the fail-closed input tests and the dedicated renderer test suite. The depth guidance is not CalcDomain's own advice: every claim is attributed to a named university Extension publication with its URL and retrieval date. Every calculation runs in your browser; nothing you type is sent to a server. See the public changelog.
Limitations
- Uneven terrain, slopes, dips and settled low spots absorb more mulch than a flat rectangle of the same measured area.
- Spreading is never perfectly uniform in practice: the depth you measure at one point is not the depth across the whole bed.
- Organic mulch settles and decomposes at rates that depend on the material, the climate and the season. No settling factor is applied here.
- Bag sizes vary by brand, product and country. A bag is only 2 ft³ if the bag says so — always use the volume printed on yours.
- Supplier practice varies: increments, minimum orders, scoop sizes, delivery radius and fees are set by the yard, not by this page.
- An area measured on a map carries the uncertainty of where you placed the vertices and of the imagery itself; it is an estimate, not a survey.
- Mulch quality, particle size, dye retention and longevity are product properties and are not estimated anywhere on this page.
- No volume is converted to a weight. Turning cubic yards into pounds or kilograms requires the bulk density of your specific product, which this calculator will not invent.
- Depth guidance varies by material texture, plant, soil drainage and region, and the published sources cited here do not all state the same range — there is no single universally correct depth.
- This is a planning estimate. Confirm bag sizes, increments, minimum orders and delivery terms with your supplier before ordering.
Frequently asked questions
How much mulch do I need?
Multiply the area by the depth you are adding: V = area × depth. In US units it collapses to cubic yards = square feet × depth in inches ÷ 324. For 200 ft² at 3 in that is 200 × 3 ÷ 324 = 1.85 cubic yards. If the bed already has mulch on it, use the difference between the depth you want and the depth already there.
How do I calculate cubic yards of mulch?
Work out the square footage, multiply by the depth in feet (inches ÷ 12) to get cubic feet, then divide by 27 because a cubic yard is 27 cubic feet. The shortcut ft² × inches ÷ 324 does the same two steps at once, since 27 × 12 = 324.
How much area does a cubic yard of mulch cover?
One cubic yard covers 324 ft² at 1 inch deep, 162 ft² at 2 inches, 108 ft² at 3 inches and 81 ft² at 4 inches. Those four numbers are just 324 divided by the depth in inches, and the table on this page is generated by the calculator's own engine rather than typed in.
How many bags of mulch are in a cubic yard?
It depends entirely on the bag. A cubic yard is 27 ft³, so it is 27 bags of 1 ft³, 18 bags of 1.5 ft³, 13.5 bags of 2 ft³ or 9 bags of 3 ft³. Note that 13.5 is the mathematical equivalent: to actually equal or exceed a cubic yard you have to buy 14 whole 2 ft³ bags, because bags do not split.
How many 2 cubic foot bags of mulch do I need?
Divide the volume you need in cubic feet by 2 and round up. For 50 ft³ that is exactly 25 bags; for 25 ft³ it is 12.5 bag-equivalents, which means 13 whole bags. This page always shows both figures, because the first one is the maths and the second one is the purchase.
How much mulch do I need for 100 square feet?
At 1 inch, 8.33 ft³ (0.31 yd³); at 2 inches, 16.67 ft³ (0.62 yd³); at 3 inches, 25 ft³ (0.93 yd³); at 4 inches, 33.33 ft³ (1.23 yd³). In 2 ft³ bags that is 5, 9, 13 and 17 whole bags.
How much mulch do I need for 500 square feet?
At 3 inches deep, 500 ft² needs 125 ft³, which is 4.63 cubic yards, or 63 whole bags of 2 ft³. At 2 inches it is 3.09 cubic yards and at 4 inches 6.17 cubic yards. The project-size table on this page shows all four depths.
How much mulch do I need for 1,000 square feet?
At 3 inches deep, 1,000 ft² needs 250 ft³ — 9.26 cubic yards, or 125 whole bags of 2 ft³. At that size bulk delivery is usually worth pricing against bags, which is what the cost comparison on this page is for.
How deep should mulch be?
There is no single correct answer, which is why this calculator asks rather than assumes. Penn State Extension gives 2 to 4 inches of coarse organic mulch around landscape trees, but only 1 to 2 inches for finely textured material; University of Maryland Extension says organic mulches should not exceed three inches, and no more than one inch over shallow-rooted plants like boxwood; University of Minnesota Extension gives 2 to 4 inches for general garden mulching. Every one of those claims is shown on the page with its source, its context and the date it was retrieved.
How do I calculate mulch for a circular bed?
Area = πr², so measure the diameter, halve it for the radius, square it and multiply by π. A 10 ft circle is π × 5² = 78.54 ft², which at 3 inches needs 19.63 ft³ — about 0.73 cubic yards, or 10 whole bags of 2 ft³. The calculator accepts either the diameter or the radius.
How do I calculate mulch for a tree ring?
A tree ring is an annulus: A = π(R² − r²), the outer circle minus the bare circle you are deliberately leaving around the trunk. With a 10 ft outer diameter and a 2 ft bare centre that is π(5² − 1²) = 75.4 ft², not 78.5 — and at 3 inches the difference is real mulch. Enter the inner measurement and the calculator excludes that ground physically rather than estimating it away.
How do I calculate mulch for an irregular bed?
Break it into pieces you can actually measure — rectangles, triangles, circles — and add them, or measure the outline on a map and enter the resulting area directly. The calculator has a mode for a sum of measured pieces, and each piece stays visible in the breakdown table instead of disappearing into one averaged number.
Can I calculate several beds at once?
Yes. Project Builder takes as many areas as the job has, each with its own name, shape, units, target depth, existing layer and quantity, and each can be included or excluded without deleting it. The total is the sum of the areas at full precision — nothing is rounded to whole bags until the very end, because rounding every bed first is how estimates drift upward.
I already have mulch. How much more do I need?
Only the difference: top-up depth = target depth − current depth. A 100 ft² bed with 1 inch already down and a 3 inch target needs 2 inches, which is 16.6666667 ft³ — 0.61728395 cubic yards, or 9 whole bags of 2 ft³. If the bed is already at or above the target, the answer for that bed is zero and the calculator says so rather than recommending a token amount.
Is it cheaper to buy mulch in bags or in bulk?
That depends on your prices, your supplier's increment and minimum, and the delivery fee — so this page asks for all of them instead of quoting an average. It costs the whole bags you would actually buy against the actual supplier order plus delivery and any fixed fee, names the cheaper option and the exact difference, and finds the break-even by walking every purchasable quantity rather than dividing one price by the other.
How much area does one bag of mulch cover?
A 2 ft³ bag covers 24 ft² at 1 inch deep, 12 ft² at 2 inches, 8 ft² at 3 inches and 6 ft² at 4 inches. For any other bag size, divide the bag volume in cubic feet by the depth in feet — or use Reverse Coverage on this page, which does it for bags, cubic yards, cubic metres or litres.
Does this calculator work in metric?
Yes, and not by converting the answer afterwards. Everything is computed in cubic metres internally, so a 10 m × 5 m bed at 7.5 cm gives 50 m² and 3.75 m³ exactly. Bag presets switch to 20, 40, 50, 60 and 70 litres, bulk pricing switches to price per cubic metre, and the same physical project shows the same physical volume in either system.
Can I use this for compost or topsoil?
The volume arithmetic is identical for any material spread at a depth, so yes for the quantity. What does not carry over is the depth guidance: the sources cited here are about mulching, and a compost topdressing is applied at a different depth for different reasons. Use your own figure and the calculator will use it.
Does the type of mulch change how much I need?
Not the volume. A cubic yard of cedar and a cubic yard of wood chips fill the same hole, so switching material on this page cannot change the geometric result — and a test enforces that. What material genuinely changes is how deep it should go (fine material is recommended shallower than coarse), how fast it settles, and what it weighs, which is why weight is never estimated here without a density.
Should I add 10% extra for settling?
Only if you decide to. This calculator defaults the planning allowance to 0% and reports it as its own line, so the geometric volume stays visible. A 10% figure that is silently baked into the total is indistinguishable from an error, and on a large job it is real money.
How much does a cubic yard of mulch weigh?
This page will not tell you, and that is deliberate. Weight is volume × bulk density, and bulk density varies enormously with material, particle size and how wet it is. Without a density figure from your specific product, any weight would be invented. Ask your supplier for the density and multiply it yourself.
Why is the mulch shortcut divided by 324?
Because one cubic yard is 27 cubic feet and one inch of depth is 1/12 of a foot, so a cubic yard spread one inch deep covers 27 ÷ (1/12) = 324 ft². That single constant is why cubic yards = square feet × depth in inches ÷ 324 works, and it is derived from the exact unit factors in this engine rather than typed in as a magic number.