Compound interest is interest earned on both your original amount and on the interest you've already earned. Enter a starting amount, interest rate, compounding frequency, and time period to see how your money grows.
Compound Interest Calculator
LiveThe compound interest formula
A is the future value, P is the starting principal, r is the annual rate (as a decimal), n is the number of times interest compounds per year, and t is time in years.
$10,000 at 6% annual interest, compounded monthly, for 10 years: A = 10000 × (1 + 0.06/12)¹²⁰ ≈ $18,193.97 — meaning about $8,193.97 in interest earned.
Step-by-step guide
- Enter your starting amount.
- Enter the annual interest rate as a percentage.
- Choose how often interest compounds — more frequent compounding grows slightly faster at the same stated rate.
- Enter the number of years you plan to leave the money invested.
Common mistakes
Frequently asked questions
Why does compounding frequency matter?
Each time interest compounds, it gets added to the balance and starts earning its own interest. Compounding monthly instead of annually, at the same stated rate, results in a slightly higher final value because interest starts earning interest sooner.
What's the difference between this and simple interest?
Simple interest is calculated only on the original principal every period. Compound interest is calculated on the principal plus any interest already earned, so it grows faster over time. See our Simple Interest Calculator to compare.
Does this include regular contributions?
No — this assumes a single lump sum with no further deposits. If you're adding money regularly, our Investment Calculator models that instead.
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