Compound Interest Calculator
Project the future value of savings or investments with compound interest.
%
Compounding
8,193.97
Formula
Examples
| Input | Result |
|---|---|
| $10,000 principal, 5% annual rate, compounded monthly, 10 years | Future value $16,470.09; interest earned $6,470.09 |
| $5,000 principal, 8% annual rate, compounded quarterly, 5 years | Future value $7,429.74; interest earned $2,429.74 |
| $1,000 principal, 10% annual rate, compounded annually, 1 year | Future value $1,100.00; interest earned $100.00 |
About this calculator
A compound interest calculator shows how an investment or deposit grows when interest earns its own interest over time. Unlike simple interest, which is calculated only on the original principal, compound interest adds each period's earnings back to the balance, so the next period earns interest on a larger amount. This snowball effect is the engine behind long-term saving and investing.
The calculation uses A = P(1 + r/n)^(nt), where A is the final amount, P is the principal, r is the annual interest rate as a decimal, n is the number of times interest compounds per year, and t is the time in years. The interest earned is simply A − P. More frequent compounding (monthly or daily rather than yearly) produces a slightly larger final balance for the same nominal rate.
To use the calculator, enter your principal, the annual interest rate, the compounding frequency (annually, quarterly, monthly, or daily), and the number of years. It returns the future value (A) and the total interest earned. Adjust the frequency or time horizon to see how compounding and patience amplify growth.
Interpret the future value as what your money becomes, and the interest as the reward for leaving it invested. The longer the time and the more frequent the compounding, the more dramatic the gap between principal and final value, especially over decades. Small differences in rate or frequency compound into large differences over long periods.
A common misconception is that compounding frequency matters more than time, when in fact time is the dominant factor. Also note this calculator assumes a constant rate and no withdrawals; real-world taxes, fees, and inflation reduce true returns. Treat the figure as a gross, pre-tax estimate rather than guaranteed spendable money.
Frequently asked questions
Simple interest is calculated only on the original principal, so it grows in a straight line. Compound interest adds each period's interest back to the balance, so future interest is earned on a growing total. Over long periods, compounding produces substantially more than simple interest.
Yes, but modestly. For the same nominal rate, monthly compounding beats annual compounding because interest is added and starts earning sooner. The difference is small over short periods but adds up over many years; time invested matters far more than frequency.
It is a quick shortcut to estimate how long money takes to double: divide 72 by the annual interest rate. At 6%, money roughly doubles in 72 ÷ 6 = 12 years. It is an approximation that works best for rates between about 4% and 12%.
No. The result is a gross, pre-tax figure assuming a fixed rate and no withdrawals. Taxes on interest and inflation both erode real purchasing power, so your effective return will be lower. Subtract an estimate for those to gauge real growth.
Use the annual nominal rate your account or investment quotes. For savings accounts and CDs this is straightforward; for investments, use a realistic expected average return rather than a best-case year. Be conservative, since overestimating the rate inflates the projected balance considerably.
This calculator grows a single lump sum. For ongoing monthly or yearly deposits, use a savings or future-value calculator that models periodic contributions, since each deposit compounds for a different length of time and changes the final balance significantly.
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