Future Value Calculator

Future value is FV = PV × (1 + r)^n. PV is the amount you have today, r is the growth rate for one period expressed as a decimal, and n is the number of periods. $10,000 at 8% a year for 10 years becomes 10000 × 1.08^10 ≈ $21,589. The piece that carries all the weight is (1 + r)^n, the growth factor. It is a pure multiplier that depends only on the rate and the time, never on the amount. That has a useful consequence: the factor for 8% over 10 years is about 2.159 whether you start with $100 or $100 million. You can compute it once and apply it to any starting sum. The one rule that must not be broken is that r and n have to use the same period. An 8% annual rate over 10 years means r = 0.08 and n = 10. If you switch to months you must use the monthly rate and the number of months — not the annual rate with a month count, which is the single most common error in time-value calculations.

Simple interest pays on the original sum forever. Compound growth pays on the accumulated balance, so each period's gain becomes part of the base for the next. The result is that the curve does not rise steadily — it accelerates. The practical consequence is that time is not a linear input. Doubling the horizon does far more than double the result: at 8%, ten years multiplies the sum by about 2.16, twenty years by about 4.66, and thirty by about 10.06. The last decade of a thirty-year run contributes more absolute growth than the first two combined, which is why an early start is worth more than a later, larger contribution. The rule of 72 is the mental shortcut: divide 72 by the percentage rate to estimate the years to double. At 8%, 72 ÷ 8 = 9 years; the exact figure is about 9.01. The approximation is good for rates roughly between 4% and 12% and drifts at the extremes, but it is close enough to sanity-check a projection in your head before trusting the calculator.

This calculator compounds once per period at the rate you enter, which is annual compounding when you use years. Real accounts often compound more frequently, and that changes the answer. A rate quoted as "6% compounded monthly" does not grow money by 6% in a year. The monthly rate is 6% ÷ 12 = 0.5%, applied twelve times: 1.005^12 ≈ 1.0617, an effective annual rate of about 6.17%. The quoted 6% is a nominal rate; the 6.17% is what actually happens. The gap widens as the rate rises and as compounding gets more frequent. This is exactly why US deposit accounts are advertised with an APY, which already includes the compounding effect and is therefore comparable across banks, while loans are advertised with an APR. When you want the honest answer from this page, enter the effective annual rate rather than a nominal one.

$21,589 in ten years is not $21,589 of today's shopping. Prices move, and a future value calculated at a nominal rate answers "how many dollars" rather than "how much can I buy". There are two clean ways to handle this and one messy one. You can work in real terms by entering a real growth rate — the nominal rate minus expected inflation — in which case the result is already expressed in today's purchasing power. Or you can work in nominal terms and separately deflate the answer by the inflation you expect. The messy option, mixing a nominal rate with an intuition about what things will cost, is where most planning errors live. A rough real rate is nominal − inflation; the exact relationship is (1 + nominal) ÷ (1 + inflation) − 1, which matters when either figure is large. Neither is a forecast — future inflation is unknown, and the US price indices that measure past inflation are published by the Bureau of Labor Statistics.

Future value is a deterministic formula. It assumes a constant rate, applied smoothly, for the whole horizon — and no investment behaves that way. Markets deliver returns in uneven bursts, and a portfolio that averages 8% over a decade may have produced -20% and +30% along the way. The formula is accurate for something contractually fixed, such as a CD held to maturity; for anything market-linked it is a scenario, not a projection. It also assumes no deposits and no withdrawals. This page projects a single lump sum forward. If you plan to add money monthly, the compound interest calculator handles the series; if you want to bring a future amount back to today, that is present value, the same equation solved for PV. Finally, the result is before taxes and fees. Investment costs compound against you in exactly the way returns compound for you, and the tax treatment depends on the account. This page is educational and is not investment or tax advice.