Investment Calculator

How to use this calculator

Pick what you want to work out. Future Value asks for a starting amount, a regular contribution, how often you invest, a time horizon and an expected annual return, and projects what the plan is worth at the end. Investment Goal takes a target instead of a contribution and solves for the amount you would need to invest each period. Time to Goal takes a target and a contribution and finds the first period the balance reaches it. Nothing else is required: fees, inflation, a simplified tax estimate, an annual contribution increase and contribution timing all sit under Advanced assumptions and start at settings that change nothing, so you can add them one at a time and watch what each one costs.

The formula, and what it assumes

Each period the balance grows by the periodic equivalent of the annual return you entered, then the contribution is added — or added first, if you chose start-of-period timing. Written as a closed form for a level contribution:

P = starting investment, PMT = contribution per period, c = contributions a year, n = c × years, EAR = the effective annual return. A fee is charged on the balance each period, the optional tax figure is applied once to the gain at the end, and inflation restates the result in today’s money without touching the nominal path. The Investment Goal and Time to Goal modes solve this same relationship backwards by bounded search, so all three answers come from one model.

Growth is applied to the whole balance once per contribution period at the effective annual return entered, and each contribution is added at the start or the end of its period as selected. Annual fees are charged on the balance each period; the optional tax figure is a single flat estimate applied to the gain at the end of the horizon; inflation is used only to restate the result in today’s money. All three modes — future value, required contribution and time to goal — run through the same simulation, and the goal and time answers are found by bounded search over it rather than by a separate formula. Historical figures quoted on this page are labelled with their source and period and are context, never a forecast.

Compounding frequency, APR versus APY and simple-versus-compound comparisons are a subject of their own; the compound interest calculator is built around them, while this page assumes the effective rate you type and concentrates on sizing a plan.

Investment return vs ROI

They answer different questions. ROI measures a return that has already happened, as a single percentage of what you put in: ROI = (gain − cost) ÷ cost × 100. It carries no time dimension — a 96.7% ROI could have taken one year or twenty.

This page projects forward instead. $10,000 at 7% for 10 years reaches $19,672, which is an ROI of 96.7% and an annualised return of 7%. The second number is the one you can compare across plans of different lengths; the first is not.

Use ROI when you are scoring a completed investment against its cost, and a projection when you are sizing a plan you have not made yet. If you want the ROI figure for something you already hold, the dedicated ROI calculator is the right tool.

What fees do to a portfolio

A fee is a percentage of the balance, so it grows exactly as the balance grows — which is why a number that looks trivial in year one is not trivial by year thirty. The figure above is the whole cost: the money handed over plus the growth that money would have earned had it stayed invested.

Worked with the calculator's own engine: $50,000 invested with $500 a month at 7% for 30 years reaches $965,339 with no fee. Add a 1% annual fee and the same plan ends at $763,501 — a difference of $201,838, or 20.9% of the fee-free result. At 0.25%, closer to a broad index fund, the cost is $55,521, or 5.8%.

Enter the fee you actually pay: for a fund that is the expense ratio, and if you use an adviser or a platform, add their percentage on top. Fees are the one assumption on this page you can check exactly rather than guess.

Inflation: nominal dollars and real purchasing power

Returns come in two flavours. Nominal is the number on the statement. Real is nominal minus inflation — what the money will actually buy. The calculator keeps them separate on purpose: the inflation rate never changes the nominal projection, it only restates it in today's money.

The gap compounds too. $10,000 plus $500 a month at 7% for 30 years projects to $660,849 nominal; at 3% inflation that is $272,261 in today's money — about 41% of the face number. Neither figure is wrong, and using the nominal one to size a retirement target is how people end up short.

A practical rule: plan the target in today's money and read the inflation-adjusted row, or plan in future dollars and inflate the target to match. Mixing the two is the common error.

What return should I use?

This is the assumption that moves the result most, and the calculator cannot supply it — nobody can. What it can do is separate two things that get confused: what markets have returned in the past, and what you choose to assume about the future.

The historical record is context, not a forecast. Over 1928–2024, US large-cap stocks returned roughly 10% a year nominal and about 7% after inflation; bonds returned far less. Those are long-run averages from Damodaran (NYU Stern) and Federal Reserve series, and they hide decades that looked nothing like the average — the table below gives the volatility alongside each figure so the spread is visible.

For a plan, most people use a number at or below the long-run real average for their mix, and then check the lower scenario rather than the base one. A useful discipline: if the plan only works at the higher scenario, it is not a plan. Enter a rate you would still be comfortable with if it turned out to be optimistic, and let the scenario range show you what the downside costs.

Long-run US asset-class returns, 1928–2024

Historical context, not a forecast. These are long-run annualised averages over 1928–2024 compiled from Damodaran (NYU Stern) and Federal Reserve series; the volatility column is there to show how little any single decade resembled the average.

Past performance does not indicate future returns, and these averages conceal decades that diverged sharply from them — equities have lost half their value in some downturns and tripled in some expansions. The diversification effect is visible in the table: stocks and bonds held together have lower volatility than stocks alone, for a modest sacrifice in return.

Using this calculator for stocks and index funds

Yes — with one thing understood. The tool models assumed future growth at a constant rate. It does not look up a ticker, it does not read market data, and it does not predict what any stock or index will do. You supply the return; the calculator applies it faithfully.

For a broad index fund that is a reasonable way to size a plan, because a diversified fund's long-run return is the thing being averaged. For a single stock it is much weaker: an individual company's outcome is not well described by a smooth average, and the calculator will happily project a number that no single stock is likely to follow.

Two settings matter more than usual here. Put the fund's expense ratio in the fee field — for index funds it is often 0.03%–0.20%, and the difference from an actively managed 0.75% is visible over decades. And if you invest a fixed amount every month, keep the contribution frequency on Monthly rather than annualising it, because when the money goes in changes the result.

Dollar-cost averaging vs lump sum

Mathematically, investing a windfall all at once has beaten spreading it over 6–12 months roughly 70% of the time in historical US data (Vanguard research, cited below). The reason is unglamorous: markets rise more often than they fall, so being invested sooner usually wins.

Psychologically it is the harder choice. Deploying $200,000 the day it arrives and watching it fall 15% the next month is a different experience from the identical loss spread over a year, and an investor who freezes and never starts does worse than either. A three-month schedule captures most of the mathematical advantage with much less of that pressure.

For ordinary monthly investing the question does not arise — paychecks arrive in instalments, so contributing monthly is not a strategy, it is just how the money shows up. Model that with the contribution field; model a windfall with the starting amount.

Worked examples

Three plans, all computed by the calculator above with the same engine that draws the chart. Change any figure in the tool and the numbers below stop matching — that is the point: they are illustrations of the method, not targets.

Example 1: starting from zero

$0 to begin, $300 a month, 7% a year, 30 years. The plan projects to $350,836. You put in $108,000 of your own money; the remaining $242,836 is growth.

Nearly 70% of the result is growth rather than contributions — and almost all of that growth accrues in the second half, because compounding works on the balance you have already built. This is why the time horizon is usually the strongest lever for someone starting out, and why a small contribution started now is hard to beat with a larger one started later.

Example 2: a lump sum plus monthly contributions

$25,000 to start, $500 a month, 7% a year, 20 years. The plan projects to $350,510 from $145,000 invested.

Split apart, the $25,000 on its own would reach $96,742 and the monthly $500 on its own would reach $253,768. The lump sum is 17% of what you put in but 28% of what you end with, because every dollar of it compounds for the full twenty years while the contributions each compound for less.

Example 3: what a 1% fee costs

$50,000 to start, $500 a month, 7% a year, 30 years — run twice, once with no fee and once with 1%.

No fee: $965,339. With 1%: $763,501. The fee costs $201,838, or 20.9% of the fee-free result, on a plan where you contributed $230,000. Set the fee to 0.25% instead and the cost falls to $55,521.

Nothing about the investments changed between those two runs — only the percentage skimmed off the balance each period. It is the clearest example on this page of a small assumption with a large consequence.

Frequently asked questions

How much will $10,000 grow in 20 years?

It depends entirely on the return you assume, which is why the calculator asks rather than deciding for you. A $10,000 lump sum with no further contributions reaches about $26,533 at 5% a year, $38,697 at 7% and $56,044 at 9% over 20 years. The spread between those three is larger than the starting amount itself — enter your own rate above and read the lower and higher scenarios alongside it.

How much do I need to invest each month to reach $1 million?

Switch to the Investment Goal mode and the calculator solves it. Starting from zero at an assumed 7% a year, reaching $1,000,000 needs about $855 a month over 30 years, $1,970 a month over 20 years, or $405 a month over 40 years. Starting with $10,000 already invested lowers the 30-year figure to about $790 a month. The horizon matters more than almost anything else in that list.

What rate of return should I assume?

One you would still be comfortable with if it turned out optimistic. Over 1928–2024 US large-cap stocks averaged roughly 10% a year nominal and about 7% after inflation, per Damodaran (NYU Stern) and Federal Reserve series — but that is historical context, not a forecast, and a bond-heavy or cash-heavy mix has returned far less. Whatever you pick, check the lower scenario the calculator shows next to it; a plan that only works at the higher scenario is not a plan.

Does this calculator include compound interest?

Yes. Growth is applied to the whole balance each period, including growth already earned, which is what compounding means. Contributions are added at the start or the end of each period as you choose, and each one compounds from the moment it goes in. If you want to explore the mechanics of compounding itself — APR versus APY, different compounding frequencies, simple versus compound interest — the dedicated compound interest calculator is built for that; this page is built for sizing a plan.

How does inflation affect investment growth?

It does not change the nominal projection at all; it changes what that projection buys. $10,000 plus $500 a month at 7% for 30 years reaches $660,849 in future dollars, which at 3% inflation is worth about $272,261 in today's money — roughly 41% of the face number. Set an inflation rate under Advanced assumptions and the calculator shows both figures side by side, and the chart can be switched to the inflation-adjusted view.

How much do fees reduce returns?

Far more than the headline percentage suggests, because a fee is charged on the balance and therefore grows with it. On $50,000 plus $500 a month at 7% over 30 years, a 1% annual fee costs $201,838 — 20.9% of the fee-free result. The same plan at 0.25% loses $55,521, or 5.8%. Enter your fund's expense ratio plus any adviser or platform charge; this is the one assumption here you can look up exactly instead of estimating.

Can I use it for stocks or index funds?

For a diversified index fund, yes — that is close to what a long-run average return describes, and it is a reasonable way to size a plan. For a single stock it is much weaker, because one company's outcome is poorly described by a smooth average. Either way the calculator models assumed future growth at a rate you supply: it does not look up prices, read market data or predict what any stock or index will do.

Are the results guaranteed?

No. The arithmetic is exact for the assumptions you entered, and that is a different claim from predicting the market. Real returns arrive unevenly, and the order they arrive in changes the outcome even when the average is identical. Use the projection to compare plans and to see which lever moves the number most, not as a forecast — and nothing on this page is investment advice.

What is the difference between investment return and ROI?

ROI measures a return that already happened, as one percentage of what you put in: (gain − cost) ÷ cost × 100. It has no time dimension, so a 96.7% ROI could have taken one year or twenty. This page projects forward and reports an annualised rate, which is comparable across plans of different lengths. $10,000 at 7% for 10 years reaches $19,672 — a 96.7% ROI and a 7% annualised return, describing the same money two different ways.

Why does my result change when I change the contribution frequency?

Because when money goes in changes how long it compounds. The same $6,000 a year invested monthly is in the market earlier than the same amount invested as one annual payment, so it earns slightly more. The expected return you enter is treated as an effective annual rate, so the rate itself does not change with frequency — only the timing does. Contribution timing, start or end of period, works the same way and sits under Advanced assumptions.

Method, assumptions and limitations

An accurate calculation of the assumptions you entered is not an accurate prediction of future markets. This tool applies one steady return to every period; real returns arrive unevenly, and the order they arrive in changes the outcome. Treat the result as a way to compare plans and to see which lever moves the number most — not as a forecast, and not as investment advice.

Assumptions

• The expected return is an effective annual rate applied evenly to every period; a nominal (APR) reading with monthly, quarterly or yearly compounding is available under Advanced assumptions › Return processing.
• Contributions are invested in full at the selected frequency, at the end of each period by default or at the start if you choose annuity-due timing.
• The annual contribution increase is applied on each contribution anniversary, not on a calendar date.
• Fees are a percentage of the balance charged pro rata each period; there is no flat account fee and no per-transaction commission.
• The tax figure is a simplified drag: a single flat rate applied once, to the positive gain at the end of the horizon. It is not a tax calculation for any jurisdiction and models no account type, bracket or holding period.
• Inflation is used only to restate results in today's money; it never alters the nominal projection.
• The horizon is rounded to whole contribution periods and capped at 100 years.
• All figures are US dollars, with no currency conversion.

Limitations

• It is a projection, not a prediction: one constant return every period, with none of the volatility a real portfolio has. Two portfolios with the same average return can end far apart depending on the order those returns arrive in.
• There is no Monte Carlo simulation and no sequence-of-returns modelling.
• No market, fund or ticker data is looked up, and no historical backtest is run — the return is the one you type.
• The tax estimate is deliberately crude and should not be used for planning around a specific account or jurisdiction.
• Withdrawals are out of scope; contributions cannot be negative.
• Deflation is not modelled: a negative inflation rate is not accepted.
• Nothing here is investment advice, and no result is guaranteed.

Sources

• Damodaran — NYU Stern Historical Returns Database — Long-run historical returns by asset class (as of May 31, 2026)
• SEC — U.S. Securities and Exchange Commission — Investor education on diversification and asset allocation (as of May 31, 2026)
• Vanguard Research — Lump sum vs dollar-cost averaging analysis (as of May 31, 2026)

Data behind the defaults

• 10.60% — S&P 500 long-run annual return · S&P Dow Jones Indices (as of December 31, 2025)
• 5.00% — 10-year U.S. Treasury yield · Federal Reserve Bank of St. Louis (FRED), based on Board of Governors H.15 data (as of September 15, 2026)
• 3.80% — U.S. inflation, 12-month change · U.S. Bureau of Labor Statistics (as of April 30, 2026)

Author: Ugo Candido · Reviewed August 20, 2026 · Engine v1.0.0 · Calculations stay in your browser; no figure you enter is sent to a server.

Reviewed according to the CalcDomain Editorial Policy & Calculator Methodology. We document formulas, edge cases, sources, update dates, and correction paths for calculator pages.

Updated August 20, 2026

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