Compound Interest Calculator

See how savings grow with compound interest, including optional monthly deposits.

A free online compound interest calculator — see how your savings grow with monthly compounding, including optional monthly deposits. Great for financial planning and long-term investing.

Starting amountAnnual interest (%)YearsMonthly deposit

Future value

181,939.67

Total contributions

100,000

Total interest

81,939.67

How to use

Enter the starting amount, annual rate, number of years, and an optional monthly deposit to see the future value, total contributions, and interest earned.

Enter the starting amount
Enter the annual rate and number of years
Add an optional monthly deposit
Read the future value and interest earned

Formula

FV = P(1+i)ⁿ + PMT × ((1+i)ⁿ − 1) ÷ i, where i = monthly rate and n = number of months.

FAQ

How is compound interest different from simple interest?

Compound interest earns interest on both the principal and previously earned interest, so it grows faster than simple interest.

How often does it compound?

It compounds monthly — the most common case for savings.