Compound Interest
Growth over time.
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About Compound Interest
The Compound Interest Calculator shows how your savings or investments grow over time. Enter a starting principal, an annual interest rate, the number of years, and how often interest compounds (annually through daily). Add an optional monthly contribution to see the effect of regular deposits. It instantly displays your final balance, total contributions, and total interest earned.
The calculator is completely free with no sign-up, and it runs entirely in your browser. Nothing you type is sent to a server or stored anywhere, so your numbers stay private on your own device. Adjust any field and the results update immediately, making it easy to compare different rates, timelines, and savings habits.
Frequently asked questions
- Is the compound interest calculator free to use?
- Yes. It is completely free with no account, sign-up, or subscription required. You can run as many calculations as you like.
- Is my data uploaded or stored anywhere?
- No. All calculations happen locally in your browser. Nothing you enter is transmitted to a server, saved, or shared, so your financial figures stay private on your device.
- How is compound interest calculated?
- The initial principal grows by the formula P(1 + r/n)^(nt), where P is the principal, r is the annual rate as a decimal, n is the number of compounding periods per year, and t is the number of years. Monthly contributions are added as a separate future-value calculation and combined with the principal.
- What does compounding frequency mean?
- Compounding frequency is how often interest is added to your balance so that it starts earning interest itself. You can choose annually, semi-annually, quarterly, monthly, or daily. More frequent compounding produces a slightly higher final balance for the same rate.
- Can I include regular monthly contributions?
- Yes. The monthly contribution field is optional. When you enter an amount, the calculator treats each deposit as made at the end of the month and adds the future value of all those contributions to your final balance.
- Does the calculator account for taxes and inflation?
- No. The result is a pre-tax estimate that does not deduct taxes, account fees, or inflation. It is intended for quick planning and comparison, not as financial advice.