Milligrams to Ounces
An ounce is 28,349.523125 milligrams. The two units sit four and a half orders of magnitude apart, which is the whole reason this conversion is awkward: anything measured in milligrams is a fraction of an ounce too small to say out loud.
Result
Exact — Both unit definitions are exact, so this relationship is exact by definition; only the displayed digits are rounded.
Round-trip check passed Converting the unrounded result back to milligrams reproduces the input within 1 part in 10¹². This is an inverse-consistency check of the engine, not an independent authority.
- Formula
oz = mg × 0.0000352739619496- Conversion factor
- 1 milligram = 0.0000352739619496 oz
- Definitions
- 1 milligram = 0.000001 kg (exact)
- 1 ounce (avoirdupois) = 0.028349523125 kg (exact)
- Definition status
- Exact
- Source
- BIPM (International Bureau of Weights and Measures) — The International System of Units (SI Brochure), 9th edition
United States — Federal Register — Refinement of Values for the Yard and the Pound (1959 international yard and pound agreement), 24 FR 5348 - Last reviewed
- 2026-08-07
- Rounding
- Auto rounding (up to 10 significant digits shown); internal values are unrounded.
Calculation receipt
- Question
- Convert 1000 milligrams to ounces (avoirdupois)
- Input
- 1000
- Interpreted as
- 1000 milligrams (mg)
- Method
- Normalize through the canonical base unit (kg) using the registry definitions, then apply display rounding last.
- Formula
- oz = mg × 0.0000352739619496
- Substitution
- 1000 × 0.0000352739619496 = 0.035273961949580414
- Steps
- Interpret the input: “1000” → 1000 milligrams.
- Normalize to the canonical base (kg): 1000 × 0.000001 = 0.001 kg.
- Convert the base value to ounces (avoirdupois): 0.001 kg ÷ 0.028349523125 = 0.035273961949580414 oz.
- Round for display only: 0.03527396195 oz (auto rounding (up to 10 significant digits shown)).
- Exact result
- 0.035273961949580414 oz (unrounded IEEE-754 double)
- Decimal result
- 0.03527396195 oz
- Verification (passed)
- Converting the unrounded result back to milligrams reproduces the input within 1 part in 10¹². This is an inverse-consistency check of the engine, not an independent authority.
- Precision
- Auto rounding (up to 10 significant digits shown); internal values are unrounded.
- Engine
- conversion-engine v1.0.0 · receipt 1.0.0
About the milligram
- Symbol
- mg
- Quantity
- Mass
- System
- SI
- Definition
- 1 milligram = 0.000001 kg
- Exactness
- Exact
- Also written
- milligramme, milligrammes
- Status
- Current
About the ounce (avoirdupois)
- Symbol
- oz
- Quantity
- Mass
- System
- International (US & Imperial)
- Definition
- 1 ounce (avoirdupois) = 0.028349523125 kg
- Note
- A mass: exactly 28.349523125 g. Not the fluid ounce (volume) and not the troy ounce.
- Exactness
- Exact
- Also written
- avoirdupois ounce
- Not the same as
- US fluid ounce; Imperial fluid ounce; troy ounce
- Status
- Current
1000 milligrams in other mass units
| Unit | Value | Symbol | System |
|---|---|---|---|
| gram | 1 | g | SI |
| kilogram | 0.001 | kg | SI |
| ounce (avoirdupois) | 0.03527396195 | oz | International (US & Imperial) |
| pound | 0.002204622622 | lb | International (US & Imperial) |
| tonne (metric ton) | 0.000001 | t | Metric (non-SI) |
| short ton (US) | 0.000001102311311 | ton (US) | US customary |
Metric & Imperial conversion chart
Every figure below is generated by the same canonical engine as the calculator — there is no separately maintained table to drift out of date. “Exact” means the relationship is exact by definition; only the displayed digits are rounded.
Length
| Unit | Equals | Unit | Equals | Status |
|---|---|---|---|---|
| 1 inch | 2.54 cm | 1 centimeter | 0.3937007874 in | Exact |
| 1 foot | 0.3048 m | 1 meter | 3.280839895 ft | Exact |
| 1 yard | 0.9144 m | 1 meter | 1.093613298 yd | Exact |
| 1 mile | 1.609344 km | 1 kilometer | 0.6213711922 mi | Exact |
Mass (weight)
| Unit | Equals | Unit | Equals | Status |
|---|---|---|---|---|
| 1 ounce (avoirdupois) | 28.34952313 g | 1 gram | 0.03527396195 oz | Exact |
| 1 pound | 0.45359237 kg | 1 kilogram | 2.204622622 lb | Exact |
| 1 stone | 6.35029318 kg | 1 kilogram | 0.1574730444 st | Exact |
| 1 short ton (US) | 0.90718474 t | 1 tonne (metric ton) | 1.102311311 ton (US) | Exact |
| 1 long ton (Imperial) | 1.016046909 t | 1 tonne (metric ton) | 0.9842065276 ton (UK) | Exact |
Volume — US and Imperial are different systems
| Unit | Equals | Unit | Equals | Status |
|---|---|---|---|---|
| 1 US fluid ounce | 29.57352956 mL | 1 milliliter | 0.0338140227 US fl oz | Exact |
| 1 Imperial fluid ounce | 28.4130625 mL | 1 milliliter | 0.03519507973 imp fl oz | Exact |
| 1 US liquid pint | 0.473176473 L | 1 liter | 2.113376419 US pt | Exact |
| 1 Imperial pint | 0.56826125 L | 1 liter | 1.759753986 imp pt | Exact |
| 1 US liquid gallon | 3.785411784 L | 1 liter | 0.2641720524 US gal | Exact |
| 1 Imperial gallon | 4.54609 L | 1 liter | 0.2199692483 imp gal | Exact |
Area
| Unit | Equals | Unit | Equals | Status |
|---|---|---|---|---|
| 1 square inch | 6.4516 cm² | 1 square centimeter | 0.15500031 in² | Exact |
| 1 square foot | 0.09290304 m² | 1 square meter | 10.76391042 ft² | Exact |
| 1 square yard | 0.83612736 m² | 1 square meter | 1.195990046 yd² | Exact |
| 1 acre | 0.4046856422 ha | 1 hectare | 2.471053815 ac | Exact |
| 1 square mile | 2.58998811 km² | 1 square kilometer | 0.3861021585 mi² | Exact |
Temperature — formulas, not multipliers
Temperature scales have different zero points, so conversion is an affine formula rather than a single factor:
| Conversion | Formula | Check |
|---|---|---|
| Celsius → Fahrenheit | °F = °C × 9/5 + 32 | 100 °C = 212 °F |
| Fahrenheit → Celsius | °C = °F × 5/9 − 17.7777777778 | 32 °F = 0 °C |
| Celsius → Kelvin | K = °C + 273.15 | 100 °C = 373.15 K |
| Kelvin → Celsius | °C = K − 273.15 | 0 K = -273.15 °C |
Metric prefixes
The full current set of SI prefixes (BIPM SI Brochure, 9th edition). A prefix scales any SI unit by a power of ten: 1 km = 10³ m, 1 μg = 10⁻⁶ g. Binary data prefixes (Ki, Mi, Gi — powers of 1024) are a separate IEC system covered in the data-storage units.
| Prefix | Symbol | Factor | Decimal |
|---|---|---|---|
| quetta | Q | 10³⁰ | |
| ronna | R | 10²⁷ | |
| yotta | Y | 10²⁴ | |
| zetta | Z | 10²¹ | |
| exa | E | 10¹⁸ | |
| peta | P | 10¹⁵ | |
| tera | T | 10¹² | |
| giga | G | 10⁹ | |
| mega | M | 10⁶ | 1000000 |
| kilo | k | 10³ | 1000 |
| hecto | h | 10² | 100 |
| deca | da | 10¹ | 10 |
| deci | d | 10⁻¹ | 0.1 |
| centi | c | 10⁻² | 0.01 |
| milli | m | 10⁻³ | 0.001 |
| micro | μ | 10⁻⁶ | 0.000001 |
| nano | n | 10⁻⁹ | |
| pico | p | 10⁻¹² | |
| femto | f | 10⁻¹⁵ | |
| atto | a | 10⁻¹⁸ | |
| zepto | z | 10⁻²¹ | |
| yocto | y | 10⁻²⁴ | |
| ronto | r | 10⁻²⁷ | |
| quecto | q | 10⁻³⁰ |
How to use the conversion calculator
1. Pick the quantity you are converting — length, weight (mass), volume, temperature, or one of sixteen more families. 2. Enter the value; typing a unit with the number (3.8m, 12 ft 6 in) sets the source unit automatically when it is unambiguous. 3. Choose the From and To units — search accepts symbols and everyday aliases like lbs, micron or nautical. 4. Read the result with its formula, factor, exactness label and source, and use the precision control if you need fixed decimals or significant figures.
Metric, Imperial and US customary units
The metric system (SI) scales every unit by powers of ten and underpins all modern definitions — since 1959 even the inch, foot, yard, mile and pound are defined exactly in metric terms. “Imperial” and “US customary” are often treated as one system, but they are not universally identical: lengths and weights match, while volumes differ materially. The Imperial gallon (4.54609 L) is about 20% larger than the US gallon (3.785411784 L), Imperial pints beat US pints, and — counterintuitively — the US fluid ounce is slightly larger than the Imperial one. Any unlabeled “gallon” or “fluid ounce” is therefore ambiguous, which is why this calculator asks instead of guessing.
Exact and approximate conversions
Whether a conversion is exact is a property of the definition, not of how many decimals you see. 1 in = 2.54 cm terminates quickly and is exact; 1 m = 3.280839895… ft has endless decimals yet is equally exact, because both derive from the same exact definition. Conventional values (the 4.184 J calorie, 9.80665 m/s² standard gravity, the 365.25-day Julian year) are exact by agreement. Genuinely approximate factors exist only where a unit rests on a measured constant, like the dalton — and no number of stored digits makes those exact. The calculator labels every result with the correct category.
How conversion factors work
Most conversions are a single multiplication: the value is multiplied by the source unit's factor to reach the quantity's canonical base (meters, kilograms, seconds…), then divided by the target unit's factor. Two families break the simple-multiplier rule. Temperature is affine — °F = °C × 9/5 + 32 — because the scales start at different zeros. Fuel consumption is reciprocal — L/100 km = 235.215 ÷ mpg (US) — because one measures distance per fuel and the other fuel per distance, so halving one doubles the other.
Common conversion mistakes
- US vs Imperial gallons and fluid ounces. A UK “40 mpg” car does about 33 mpg in US gallons; a US pint of beer is 20% smaller than a UK pint. Always label the system.
- Ounce vs fluid ounce. oz is mass (28.35 g); fl oz is volume (29.57 mL US / 28.41 mL Imperial). They only coincide, roughly, for water.
- Mass vs volume. Grams cannot become milliliters without a density. A cup of flour and a cup of honey weigh very different amounts.
- Tonne vs short ton vs long ton. 1000 kg vs 907.18474 kg vs 1016.0469088 kg — an unlabeled “ton” can be off by more than 10%.
- kB vs KiB. Decimal 1000-based and binary 1024-based prefixes diverge by 7.4% at the terabyte scale — the “missing space” on a new drive.
- Mass vs force. Kilograms convert to pounds (mass), not to newtons or pounds-force; weight needs gravity (1 kgf = 9.80665 N by convention).
- US survey vs international foot. They differ by 2 ppm — irrelevant for a room, material for state-plane coordinates; the survey foot was deprecated in 2023.
- Regional cooking measures. A metric cup is 250 mL, a US cup 236.59 mL, an Australian tablespoon 20 mL vs 15 mL elsewhere.
- Rounding too early. Convert with the full factor and round once at the end — chaining rounded factors compounds the error. This engine never rounds internally.
A short history
The meter began in 1795 as one ten-millionth of the pole-to-equator distance and is now defined by the speed of light; the kilogram shed its physical prototype in 2019 for a definition via the Planck constant. The 1959 international yard-and-pound agreement ended centuries of slightly different national inches by fixing 1 yd = 0.9144 m and 1 lb = 0.45359237 kg exactly — the reason today's US and UK lengths agree while their older, separately standardized volume measures still differ.
How CalcDomain verifies unit conversions
- Every unit belongs to exactly one semantic quantity; compatibility is decided by quantity, never by raw dimensions, so energy≠torque and mass≠volume.
- Values are normalized through the quantity's canonical base unit (meter, kilogram, kelvin, joule…) — never through chained pairwise factors.
- Each definition cites a named authoritative reference: BIPM SI Brochure, NIST SP 811 / Handbook 44, the 1959 US yard-and-pound refinement, the UK Weights and Measures Act 1985, ISO/IEC 80000, IAU resolutions, CODATA.
- Exact relationships are stored at full definitional precision; nothing is pre-rounded for storage.
- Display rounding happens last and is recorded in the receipt; the unrounded value is always shown alongside.
- Ambiguous terms (gallon, ton, fluid ounce, cup, horsepower, mil, kB…) stay distinct — the calculator asks which variant you mean.
- The server-rendered result and the in-browser result come from the same engine source, so they cannot disagree.
- Automated tests pin the exact reference vectors (1 in = 2.54 cm, 1 lb = 0.45359237 kg, 1 US gal = 3.785411784 L, 0 °C = 32 °F, 1 mL ≈ 0.0338140227 US fl oz) plus identity and round-trip invariants for every unit on every build.
- Source metadata is reviewable on the page — every factor links to the document that defines it.
Author: Ugo Candido · Last reviewed: · Engine: conversion-engine v1.0.0 · Every conversion runs in your browser; values are never sent to a server. The round-trip check is an internal consistency check, not third-party review. See the public changelog.
Authoritative sources
Every unit definition in the registry cites one of these primary references. No conversion website is ever used as an authority for a constant.
- BIPM (International Bureau of Weights and Measures) — The International System of Units (SI Brochure), 9th edition
- NIST (National Institute of Standards and Technology) — Special Publication 811 — Guide for the Use of the International System of Units, Appendix B
- NIST Office of Weights and Measures — Handbook 44, Appendix C — General Tables of Units of Measurement
- United States — Federal Register — Refinement of Values for the Yard and the Pound (1959 international yard and pound agreement), 24 FR 5348
- United Kingdom — legislation.gov.uk — Weights and Measures Act 1985, Schedule 1
- ISO (International Organization for Standardization) — ISO 80000-3 — Quantities and units, Part 3: Space and time
- IEC (International Electrotechnical Commission) — IEC 80000-13 — Quantities and units, Part 13: Information science and technology
- IAU (International Astronomical Union) — IAU 2012 Resolution B2 (astronomical unit) and 2015 Resolution B2 (parsec relation)
- CODATA / NIST Fundamental Physical Constants — CODATA Internationally Recommended Values of the Fundamental Physical Constants
- ISO — ISO 2533:1975 — Standard Atmosphere
Frequently asked questions
How many milligrams are in an ounce?
28,349.523125 mg, exactly. It follows from the ounce being a sixteenth of the pound and the pound being defined as exactly 453.59237 grams, so the figure terminates rather than repeating.
How many milligrams are in a gram?
Exactly 1,000. The prefix 'milli' means a thousandth, so the step is a decimal shift with no factor to remember — which is precisely what the ounce does not give you.
Can I convert a mg/kg dose to ounces?
No. A dose in milligrams per kilogram is a rate: it tells you how much drug per unit of body weight, and it only becomes a mass once you multiply by an actual weight. Convert the resulting mass if you need to, never the rate.
Why do supplements use milligrams rather than ounces?
Because the quantities are tiny and the numbers stay legible. 400 mg reads cleanly; 0.0141 oz does not, and a misplaced zero in it is far harder to notice. Milligrams also line up with the doses used in research, so a label can be compared with a study without conversion.
Is a troy ounce different here too?
Yes — 31,103.4768 mg against 28,349.523125. Precious metals are weighed in troy ounces, so a gram-scale weight of gold converted with this page's factor reads about 9.7% low.
What about micrograms?
A microgram is a thousandth of a milligram, so an ounce is 28,349,523.125 µg. Vitamin labels move between mg and µg freely — B12 in micrograms, vitamin C in milligrams — and the thousand-fold step between them is the most common labelling error worth checking.