Compound Interest Calculator

The Compound Interest Calculator projects how a sum of money grows over time when interest is reinvested.

Enter a starting amount, an annual interest rate, a number of years and how often interest compounds, and it shows the final balance, the total you have paid in and the interest earned on top.

You can also add a regular monthly contribution to model a savings habit, and each contribution begins earning interest from the month it lands.

Compounding is often called the most powerful force in finance because interest earns interest: the longer the horizon and the more frequent the compounding, the more the curve bends upward.

Seeing the gap between what you contribute and what you end up with makes the case for starting early far more vividly than any rule of thumb.

The tool supports annual, quarterly, monthly and daily compounding so you can match a specific savings or investment product, and it steps through the projection month by month for accuracy.

All the maths happens in your browser, so the amounts you model — your savings, your goals — are never sent anywhere or stored, and it works offline.

Money values are rounded to two decimal places, and the result updates instantly as you adjust the inputs, making it easy to test scenarios: a higher contribution, a longer term, or a better rate.