Compound Interest Calculator
See how your money can grow with compound interest. Enter an initial investment, annual interest rate, time horizon and optional monthly contribution to project your future value and total interest earned.
How it works
A is the future value, P the initial principal, r the annual rate, n the number of compounding periods per year, t the years, and PMT the contribution per period. Compounding means you earn interest on previously earned interest.
A = P(1 + r/n)^(nt) + PMT · ((1 + r/n)^(nt) − 1) ÷ (r/n)Worked examples
Long-term growth
10,000 invested at 7% compounded monthly grows to about 40,387 after 20 years, even with no further contributions.
With contributions
Adding 200 per month to that same account dramatically increases the ending balance.
Frequently asked questions
What is compound interest?
Compound interest is interest earned on both your original principal and the interest that has already accumulated.
How does compounding frequency matter?
More frequent compounding (e.g., monthly vs annually) yields slightly higher returns at the same rate.
What is the difference between simple and compound interest?
Simple interest is paid only on the principal, while compound interest also pays on accumulated interest.
Results are estimates provided for information only and do not constitute financial, legal or tax advice. Consult a qualified professional before making financial decisions.
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