Compound Interest Calculator

Period-by-period compounding: each period, interest = balance × (rate / n), then balance += interest + contribution_per_period. n is the compounding frequency per year.

It's converted to a per-period contribution by 'monthly × 12 / n' so the annual total stays the same regardless of compounding frequency.

No. The result is the nominal balance before taxes and before adjusting for inflation. To see real purchasing power, subtract your expected inflation rate from your interest rate before entering.

Yes — enter a negative rate to model a depreciating balance, like a fund losing value.

After. Each period the balance earns interest first, then the contribution is added — an ordinary annuity, which is what a payroll deduction landing at month end actually looks like. Paying at the start of each period instead would earn one extra period of interest on every deposit: A starting balance of 10,000 plus 500 a month at 7% for 30 years comes to 691,150 here and 694,709 the other way, a difference of about 0.5%. If your deposits genuinely land on day one, treat the figure as a slight underestimate.

Far less than the rate or the time does. 10,000 at 7% for 30 years grows to 76,123 compounded annually, 80,192 quarterly, 81,165 monthly and 81,645 daily — the whole span from annual to daily is under 8%, and monthly to daily is 0.6%. Continuous compounding is the ceiling and daily is already almost on it. Spend your attention on the rate and the years; the frequency dropdown is a rounding detail by comparison.