About the Compound Interest Calculator
Compound interest is interest earned on interest. This calculator shows what an initial deposit plus regular contributions will grow to, how much of the final balance is interest, and the balance at the end of each year.
Choose how often interest compounds (daily to annually) and how often you contribute — they don’t need to match.
How does the Compound Interest Calculator work?
Each period, interest is added to the balance, and the next period’s interest is calculated on the larger balance. The more often interest compounds, the slightly higher the effective annual rate.
When you contribute at a different frequency from compounding, the calculator converts the rate to an equivalent rate per contribution period so the result matches true compounding.
Compound Interest Calculator formula
A = P(1 + r/n)^(nt) + PMT × [((1 + i)^(kt) − 1) ÷ i]
where i = (1 + r/n)^(n/k) − 1P is the starting amount, r the annual rate, n compounding periods per year, t years, PMT the contribution made k times a year.
Example
$10,000 at 5% compounded monthly for 10 years grows to about $16,470 with no contributions. Adding $200 a month takes it to about $47,530.