Interest calculator
Compare simple interest, compound interest with annual to daily compounding, and a monthly savings projection with month-end deposits.
Uses simple annual interest. Taxes, fees, and any provider-specific compounding are not included.
Formula estimate only. Rates, taxes, and legal rules vary by jurisdiction.
What to know
The interest tools answer one question three ways: how much will money be worth later. Simple interest, compound interest and monthly savings all take a rate in percent per year and a term in years, and each shows the final value, the amount put in and the interest earned.
Choose simple interest when interest is paid on the original amount only, as with many fixed-term loans or bonds that pay out coupons: P x (1 + r x years). Choose compound interest when earned interest is added to the balance and also earns interest, with annual, quarterly, monthly or daily compounding.
Choose the savings projection when you add the same deposit every month. It assumes the deposit arrives at the end of each month and compounds monthly at the annual rate divided by 12, using the future value of an ordinary annuity.
On 1,000,000 at 5 percent for 3 years the three give different pictures: simple interest ends at 1,150,000, annual compounding at 1,157,625, and monthly compounding at 1,161,472.23. Amounts use USD, KRW, JPY, CNY or EUR, and taxes and fees are excluded.
A useful rule of thumb is the rule of 72: at 6 percent compounded yearly, money doubles in roughly 12 years. The compound page lets you test it by entering 12 years and reading a multiple close to 2.01.
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How to use Interest calculator
- Decide between a lump sum (simple or compound) and regular deposits (savings).
- Enter the amounts and an Annual rate such as 5 with 3 years.
- For compound interest, pick the compounding frequency.
- Compare the end values and the Interest earned line across the three pages.
Quick answers
Which page should I use for a bank deposit?
Compound interest if the bank capitalises interest, simple interest if it pays on the original deposit only. Check the product terms.
Why is compound interest larger than simple interest?
Earned interest is added to the balance and earns interest itself, so each period starts from a larger amount than the last.
Does the rate mean per year?
Yes. All three pages take an annual percentage rate and a term in years, and the term can be fractional, for example 1.5.