Investment Calculator

This calculator projects how an initial investment, plus a fixed contribution every month, could grow over time — assuming a constant annual return that you choose. It uses the same time-value-of-money math behind most investment projections: your money grows on itself, and every contribution you add gets the same chance to grow for however long is left on your time horizon.

You supply the expected annual return yourself. This tool deliberately does not suggest a number — real investment returns depend entirely on what you invest in, and vary significantly from year to year, so any single figure presented here would be a guess dressed up as guidance. Base your assumption on your own research into the specific investments you're considering, or on advice from a qualified financial advisor.

Treat the result as a hypothetical illustration, not a forecast or a promise. It assumes a perfectly constant return every year, which real markets never actually deliver, and it doesn't subtract fees, taxes, or inflation. Use it to compare scenarios — a bigger monthly contribution, a longer time horizon, a different return assumption — rather than to predict an exact future balance. Nothing here is financial advice or a recommendation to invest.

A worked example

Say you start with a $5,000 initial investment, contribute $300 every month, and assume a 7% expected annual return for 20 years. Plugging into the formula gives a projected balance of $176,471.69. Of that, $77,000 came directly from your own contributions ($5,000 + $300 × 240 months), and the remaining $99,471.69 is projected growth — in this example, growth outweighs your own contributions by more than 2 to 1, largely a function of time: the earliest contributions had two full decades to compound, while the last ones barely had any time to grow at all.

A common misconception

An "average" annual return and a guaranteed, steady return are not the same thing, even though this calculator's constant-rate math can make them look interchangeable. Two investments can post the exact same average annual return over 20 years and still leave you with very different final balances, depending on when the good years and bad years actually happened — a pattern often called sequence-of-returns risk. A portfolio that loses money early, before most contributions have gone in, tends to recover better than one that loses money late, after a large balance has already built up — timing matters in a way a single constant "expected return" figure can't capture.

Where the growth assumption breaks down

This tool deliberately doesn't suggest a return figure — real returns vary by asset class, and no single defensible number applies to "investing" in general. It also doesn't subtract fees (fund expense ratios, brokerage or advisor fees), which compound against you the same way returns compound for you, quietly eating into the final balance over a multi-decade horizon even at seemingly small annual percentages. Taxes on gains and dividends, and inflation eroding what that future balance can actually buy, are left out too — reasons the number shown here is best read as a hypothetical ceiling on a "smooth" outcome, not a number to expect exactly.

How to use this projection

Investing a fixed amount every month, the way this calculator's monthly-contribution field works, is generally called dollar-cost averaging — per the SEC's investor.gov, it means buying at whatever price the market happens to offer each period rather than trying to time a single lump-sum entry, which smooths out the effect of short-term price swings without changing the underlying return your investments earn. Use this tool to compare scenarios — a larger contribution, a longer horizon, a different return assumption — and treat the gap between "contributions" and "growth" in your result as a reminder of how much of long-term investing's payoff depends on time in the market, not the size of any one contribution.

Expected return vs. actual market return

The rate you enter is an assumption you supply, not a benchmark this tool implies or endorses. Compound annual growth rate (CAGR) — the standard way analysts describe how an investment actually performed over a past multi-year period, calculated as (ending value ÷ starting value)^(1/years) − 1 — measures history after the fact; the "expected annual return" field on this calculator asks you to guess at the future instead, which is an inherently less certain exercise. If you're benchmarking an assumption, comparing it to a real investment's historical CAGR over a similar length of time is a more grounded starting point than picking a round number.