Compound Interest Calculator
Watch a starting balance and regular monthly deposits grow over time.
| Future value | $95,769.94 |
|---|---|
| Total contributions | $53,000.00 |
| Interest earned | $42,769.94 |
How to use it
- Enter what you have now and what you will add each month.
- Enter the yearly rate (a savings APY, or an assumed long-run return).
- Pick how often interest compounds. Bank accounts usually compound daily or monthly.
Formula
Without deposits: A = P × (1 + r ÷ k)^(k × t)- With monthly deposits we add each deposit at the end of the month and grow the balance at the monthly rate equivalent to compounding k times a year.
Example
$10,000 at 12% compounded monthly for one year grows to 10,000 × (1.01)^12 ≈ $11,268.25. Compounded yearly it would be $11,200. The extra $68 is interest earned on interest.
Questions
What is the rule of 72?
Divide 72 by the yearly rate to estimate how many years it takes money to double. At 6%, about 12 years.
Are investment returns guaranteed?
No. Stock returns vary year to year; a fixed rate here shows an average path, not a promise.
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Last reviewed 2026-10-10. Found a mistake? Tell us.