Compound Interest Calculator
See how your money grows over time when interest compounds. Enter a starting amount, an annual interest rate, the number of years, how often interest compounds and any regular monthly contribution, and the calculator projects your future balance and the total interest earned.
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Future balance
$144,330.41
Total contributions$58,000.00
Total interest earned$86,330.41
How it works
The compound interest formula for a lump sum is:
A = P × (1 + r ÷ n)n × t
where A is the final amount, P is the principal, r is the annual rate, n is the number of compounding periods per year and t is the number of years. When you add regular monthly contributions, each deposit also earns compound interest for the remaining time.
Frequently asked questions
What is compound interest?
Compound interest is interest earned on both your original money and on the interest already added, so your balance grows faster over time than with simple interest.
How does compounding frequency matter?
More frequent compounding (monthly or daily versus yearly) produces slightly more growth, because interest is added and starts earning sooner.
Do monthly contributions make a big difference?
Yes. Regular contributions plus compounding are the main driver of long term growth, often outweighing the interest rate itself.