Compound Interest Calculator
See how your savings or investment grows with compound interest and regular contributions.
How to use Compound Interest Calculator
- Enter your starting balance (principal).
- Enter the annual interest rate and how often it compounds.
- Optionally add a regular contribution — this is added at the end of each compounding period.
- Enter the number of years to project, and your final balance updates instantly.
About this tool
The Compound Interest Calculator projects how an initial deposit grows over time when interest compounds at a chosen frequency, with an optional regular contribution added each period. It shows the final balance, how much you contributed in total, and how much of that growth came purely from interest. All calculations run instantly in your browser — nothing is uploaded or sent to a server.
Frequently Asked Questions
What is compound interest?
Compound interest is interest calculated on both the original principal and the interest already earned. Because each period's interest gets added to the balance before the next period's interest is calculated, growth accelerates over time compared to simple interest.
How does compounding frequency affect the result?
More frequent compounding (daily vs. annually) produces a slightly higher final balance for the same nominal annual rate, because interest starts earning its own interest sooner. The difference is usually small for typical savings rates, but grows with higher rates or longer time periods.
When are contributions added?
This calculator assumes contributions are added at the end of each compounding period (an 'ordinary annuity'), which is how most savings accounts and investment plans work.