Free money calculator
See how an initial investment and regular monthly contributions may grow over time.
Last updated: October 2026
Illustration only. Actual investment returns fluctuate and may be negative.
Compound growth means returns are calculated on both your original principal and previously accumulated returns. Regular contributions can have a major effect over long periods.
Compare conservative and optimistic return assumptions instead of relying on one forecast. This calculator does not include taxes, fees, inflation, or market volatility.
Method modeled after the educational inputs used by the SEC Investor.gov calculator.
It projects how a starting amount plus regular monthly contributions could grow over time when returns compound at a chosen frequency. It separates the total future value into what you actually contributed versus what came from growth, which makes it easier to see how much of an investment goal is realistic to reach through contributions alone versus how much depends on market returns.
Starting with $10,000 and contributing $500 a month for 20 years at an assumed 7% annual return, compounded monthly, projects to roughly $300,000. Of that total, about $130,000 comes from the $10,000 starting balance plus contributions, and the remaining $170,000 comes from compound growth — illustrating why starting early and contributing consistently tends to matter more over long horizons than the exact starting amount.
It changes how often earned interest is added back to the balance so it can itself start earning returns. More frequent compounding produces a slightly higher future value at the same nominal annual rate, though the difference is usually modest.
Comparing a conservative and an optimistic assumption side by side gives a more realistic sense of the range of outcomes than relying on a single number, since real investment returns vary from year to year.
No. The result is shown in nominal future dollars. If you want a rough sense of purchasing power, you can separately reduce the projected result by an assumed inflation rate.
The inputs are modeled after the educational structure used by the SEC's Investor.gov compound interest calculator, adapted here with a simpler interface.
In depth
Compound interest means earning returns on earlier returns, not just on what you put in. The effect is small in early years and large later, which is why the time horizon matters more than almost any other input. This section explains the math behind the calculator above and how to use it without fooling yourself.
For a lump sum, future value = P × (1 + r/n)n×t, where P is the starting amount, r the annual rate, n the number of compounding periods per year and t the number of years. With regular deposits, the calculator also adds each monthly contribution and lets it compound from that point on.
| Years | Balance | Money you put in | Growth |
|---|---|---|---|
| 10 | about $72,000 | $46,000 | about $26,000 |
| 20 | about $197,000 | $82,000 | about $115,000 |
| 30 | about $447,000 | $118,000 | about $329,000 |
Going from 20 to 30 years adds only $36,000 of deposits but about $250,000 to the balance. Starting earlier usually beats contributing more later.
$10,000 at 6% for 10 years grows to about $17,908 with annual compounding, $18,194 with monthly compounding, and $18,220 with daily compounding. The rate and the number of years matter far more than the frequency. When comparing savings accounts, the APY already includes compounding, so compare APYs directly.
Divide 72 by the annual rate to estimate the years needed to double your money: about 12 years at 6% and 8 years at 9%. The exact answers are 11.9 and 8.0 years, so the shortcut is close enough for mental math.
To cross-check a result, the SEC's investor education site offers an independent calculator.
Figures checked October 2026. Tax rules change; confirm with the linked official pages before filing or signing anything.