See how your savings or investment grows over time, with optional regular contributions and a full year-by-year breakdown.
| Year | Deposits | Interest | End balance |
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Compound interest is interest calculated not just on your original investment, but also on the interest that investment has already earned. Each time interest is added to your balance, future interest is calculated on that larger amount, which is why growth accelerates the longer money is left to compound, often described as "interest earning interest."
This calculator projects how an initial investment grows over time, optionally with regular contributions added along the way, and shows exactly how much of your ending balance came from your own money versus interest earned.
The same annual interest rate produces a slightly different result depending on how often it compounds. Compounding monthly grows your balance a bit faster than compounding annually, because interest gets added to the balance sooner and starts earning its own interest that much earlier. Daily or continuous compounding pushes this effect to its practical limit, though the difference between monthly and daily compounding is usually small for typical rates and timeframes.
Adding even modest regular contributions can dramatically increase your ending balance compared to a single lump-sum investment, since each new contribution gets its own runway to compound. Contributing at the start of each period rather than the end gives that period's contribution slightly more time to earn interest, resulting in a marginally higher ending balance over many periods, though the difference is usually small relative to the overall effect of contributing regularly at all.
A well-known shortcut for estimating how long it takes an investment to double is to divide 72 by your annual interest rate. At 6% annual growth, for example, 72 ÷ 6 = 12, meaning your money would roughly double in about 12 years. It's an approximation, not an exact calculation, but it's a handy way to build intuition for how rate and time interact.
No, this calculator assumes a constant annual rate for illustration. Real investments (stocks, mutual funds) have returns that vary year to year, savings accounts and CDs typically offer more predictable, though usually lower, rates.
No, the ending balance shown is the nominal future value, before any taxes on gains and without adjusting for inflation's effect on purchasing power. For inflation-adjusted comparisons, pair this with the Inflation Calculator.
Simple interest is calculated only on the original principal every period, so it grows at a constant, linear rate. Compound interest is calculated on the principal plus all previously earned interest, so it grows faster over time. For a pure comparison, see the Simple Interest Calculator.
This calculator is built for growing a balance through contributions. For modeling regular withdrawals from a balance, such as in retirement, a dedicated withdrawal or annuity calculator would be more appropriate.
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