How to use the compound interest calculator
- Enter your starting amount and any monthly deposit.
- Enter the expected annual rate, the number of years and the compounding frequency.
- Press Calculate growth to see the final balance and interest earned.
How it works
Compound interest means you earn interest on your earlier interest as well as on the original amount. The basic formula is A = P × (1 + r ÷ n)n × t, where P is the starting amount, r is the annual rate, n is the number of compounding periods a year and t is the number of years.
This calculator also adds your monthly deposit at the end of each month, so you can see how regular saving builds up over time. A higher rate, more frequent compounding and a longer time all increase the result, with time having the largest effect.
Example
10,000 at 7% a year, compounded monthly for 10 years with no deposits, grows to about 20,097, which means about 10,097 of the total is interest.