Compound interest calculator
Free compound interest calculator with instant results. Add monthly contributions, choose any compounding frequency, and see a year-by-year growth breakdown privately.
How to use
- Enter your starting principal. Type the amount you are starting with and choose your currency from the currency selector so every result displays in the units you want.
- Set the rate and number of years. Enter the annual interest rate as a percentage and the number of years you want to project the balance forward.
- Choose a compounding frequency. Pick daily, monthly, quarterly, or annually. More frequent compounding adds interest to the balance more often, which slightly increases growth.
- Add an optional monthly contribution. If you plan to deposit a fixed amount each month, enter it. Leave it blank to model a lump sum that simply grows on its own.
- Read your results and breakdown. View future value, total contributions, and total interest earned, then scroll the year-by-year breakdown to see how the balance builds each year.
Features
- Instant, private results. Calculations run locally in your browser the moment you change an input. Nothing is uploaded, and there is no account or sign-up required.
- Flexible compounding options. Switch between daily, monthly, quarterly, and annual compounding to see exactly how frequency changes your final balance.
- Regular contributions supported. Add an optional monthly deposit to model ongoing saving, not just a one-time lump sum, for a more realistic projection.
- Year-by-year breakdown. A growth schedule shows the balance, contributions, and interest for each year so you can watch compounding build over time.
- Universal currency selector. The math is currency-agnostic and a currency selector formats every figure in the units you choose, from dollars to euros to anything else.
When to use it
- Estimating how a lump-sum savings deposit could grow over five, ten, or twenty years.
- Projecting a long-term savings goal when you add a fixed amount every month.
- Comparing how daily versus annual compounding affects the same balance.
- Teaching or learning how compound interest works using a clear year-by-year schedule.
- Running quick what-if scenarios with different rates and time horizons before talking to a professional.
Is it private?
The values you enter are processed locally in your browser and are never uploaded.
Frequently asked questions
Is this compound interest calculator free?
Yes, it is completely free to use with no limits and no sign-up. You can run as many calculations as you like.
Is my data private? Does anything get uploaded?
Everything is calculated locally in your browser. The numbers you enter are never sent to a server or uploaded anywhere, so your inputs stay on your device.
Is this financial advice?
No. This tool is educational only and does not provide financial advice. Results are estimates based on the values you enter and assume a constant rate. For decisions about your money, consult a qualified professional.
How is compound interest calculated?
For a lump sum, the future value is principal times (1 + rate/n) raised to the power of n times years, where n is the number of compounding periods per year. When you add monthly contributions, each deposit also earns interest from the date it is added, and the calculator sums all of those growing balances for you.
What does compounding frequency actually change?
Compounding frequency is how often earned interest is added back to the balance. The more often this happens, the sooner new interest starts earning its own interest, so daily compounding yields slightly more than annual compounding at the same stated rate.
Does it account for taxes, fees, or inflation?
No. The calculator shows nominal growth at the rate you enter and does not deduct taxes, fees, or inflation. If you want a more conservative view, you can enter a lower rate to approximate a real, after-cost return.
What is the difference between total contributions and total interest?
Total contributions is the money you put in, your starting principal plus every monthly deposit. Total interest earned is everything above that, the growth created by compounding. Together they add up to the future value.
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