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Free Compound Interest Calculator
Work out how savings or investments grow when interest earns interest, with regular deposits.
Your starting amount and monthly contributions grow at the interest rate you enter, with interest added back at the compounding frequency you choose, from daily to yearly. The tool shows the final balance, how much you put in, the interest earned, the effective yearly yield (APY) and a balance for each year.
How to use the Compound Interest Calculator
- Enter your starting amount, regular contribution, expected return and time period.
- Read the end value and the split between money you put in and growth.
- Try a lower return as well as a higher one, because real markets are uneven.
About the Compound Interest Calculator
Work out how savings or investments grow when interest earns interest, with regular deposits.
Time and consistency do most of the work in saving and investing. Running the numbers shows how small changes in rate, term or contribution add up.
Getting started with the Compound Interest Calculator
Using the compound interest calculator takes a minute or two. Your entries are saved in this browser, so you can come back later and carry on.
Tips for better results
Time matters more than size. Try the same numbers with a few extra years, then try a higher monthly contribution, and compare how much of the final balance is interest. Use the inflation box to see the result in today's money.
Treat the result as an illustration, not a promise. Returns vary year to year.
Fees and inflation reduce real growth, so consider both when planning.
Privacy and where your data goes
Everything you type into the compound interest calculator stays on your own device. Zapxa does not receive your numbers or documents. If you clear your browser data, your saved entries will be removed, so download a PDF of anything you want to keep.
Frequently asked questions
What is compound interest?
Compound interest is interest paid on both your original money and the interest already added. Each period the balance is a little larger, so growth speeds up over time.
Does the compounding frequency matter much?
Slightly. Daily compounding gives a bit more than yearly at the same rate, which is why the tool shows the effective yearly yield (APY). Time and the rate matter far more.
Are deposits made at the start or end of each month?
They are added at the end of each month, after that month's interest. Deposits at the start of the month would give a slightly higher result.
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