Compound Interest Calculator
See how your savings grow with compounding interest and regular contributions.
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About the Compound Interest Calculator
Find out how powerful compounding really is. Enter your starting principal, annual interest rate, time horizon, compounding frequency, and any monthly contribution to see your projected final balance, your total contributions, and the interest earned. Great for planning savings, investments, and retirement goals.
How to use the Compound Interest Calculator
- 1Enter your starting principal (your initial deposit).
- 2Type the expected annual interest rate.
- 3Choose how many years you'll let the money grow.
- 4Pick a compounding frequency and (optionally) a monthly contribution.
Why use our Compound Interest Calculator
Flexible compounding
Annually, quarterly, monthly, or daily — modeled with the standard A = P(1 + r/n)^(nt) formula.
Monthly contributions
Adds the future value of a recurring monthly deposit to your final balance.
Clear breakdown
See exactly how much is contributions versus interest earned.
Private by design
Your numbers are calculated locally and never uploaded.
Frequently asked questions
What is compound interest?+
Compound interest is interest calculated on both your original deposit and on the interest already earned. Over long periods, it grows your savings much faster than simple interest.
How does compounding frequency matter?+
More frequent compounding (e.g. daily vs annually) earns slightly more interest because each interest payment starts earning interest sooner. The effect is small for short horizons and meaningful over many years.
Are the monthly contributions added before or after interest?+
We model contributions made at the end of each compounding period (an ordinary annuity), which is the standard assumption for most savings accounts.
Are returns guaranteed?+
No. This is a mathematical projection assuming a fixed rate. Real-world investments fluctuate. Use this as a planning tool, not a guarantee.