Compound Interest Calculator

Interest earned on both your money and the interest it has already earned. $1,000 at 10% a year becomes $1,100 after one year and $1,210 after two, because the second year's interest is also paid on the first year's $100.

The nominal rate is the headline annual rate. The effective annual rate includes compounding within the year: 6% compounded monthly is (1 + 0.06/12)^12 − 1 = 6.17% effective. Enter the nominal rate and the calculator shows the effective one.

Interest builds up day by day in proportion to how long each deposit has been in the account, and is added at each compounding date. A deposit made halfway through the year earns half a year's interest — it isn't treated as if the rate were split into twelve monthly steps.

Choose start if you pay in at the beginning of each month (for example on payday), end if you pay in at the end. Deposits at the start earn slightly more because they're invested longer.

The final balance divided by the price rise from the inflation rate you enter, compounded over the years. It shows roughly what the future amount would buy now — it depends entirely on your inflation assumption.

At 7% a year compounded monthly, $200 paid in at the end of every month for 30 years grows to about $243,994. You pay in $72,000; the other $171,994 is interest. The result depends heavily on the rate and the number of years, so try your own figures.

Simple interest is paid only on the original amount; compound interest is also paid on interest already earned. $10,000 at 5% for 10 years earns $5,000 of simple interest, but $6,288.95 compounded once a year.

Only a little. $10,000 at 5% for 10 years grows to $16,288.95 compounded yearly, $16,470.09 monthly and $16,486.65 daily. The effective annual rate goes from 5% to 5.12% and 5.13%. The rate itself and how long you save matter far more.

Yes. APY (annual percentage yield), which banks quote on savings accounts, is the effective annual rate: the nominal rate with compounding included. If your bank quotes an APY, enter it with yearly compounding; if it quotes a nominal rate and a compounding frequency, enter both.

A shortcut for how long money takes to double: divide 72 by the annual rate. At 8% that's 72 ÷ 8 = 9 years; the exact figure with yearly compounding is 9.01 years. It works best for rates between about 4% and 12%.

Yes. The CSV button downloads each year's total contributed, interest earned to date, balance and balance in today's money, ready for Excel or Google Sheets. Copy puts a one-line summary on your clipboard.

No. It's a projection with a constant rate. Real savings and investment returns change over time, and taxes and fees aren't included.