Compound Interest Calculator
Project how savings grow with compound interest and optional regular deposits. Choose compounding frequency, contribution amount and how often you add money — see future value, total contributions and interest earned instantly.
Starting balance
Amount added each month
Frequently asked questions
What is compound interest?
Compound interest means you earn interest on both your original principal and on interest already credited. Over time that “interest on interest” can grow balances faster than simple interest, which only applies to the principal.
How do regular contributions affect the result?
Each deposit is added to the balance and then compounds with the rest. This calculator maps your contribution amount and frequency onto each compounding period, then uses the standard future-value-of-an-annuity formula (deposits at the end of each period).
Does compounding frequency matter?
Yes. More frequent compounding (for example monthly instead of annually) applies interest more often at a smaller periodic rate. Holding the annual rate fixed, higher frequency usually produces a slightly larger future value.
Is this financial advice?
No. Results are mathematical estimates based on a fixed rate and schedule. Real returns, fees, taxes and market changes are not modeled. Use this for planning illustrations only.