Compound Interest Calculator

Seeing what a savings account, a CD or an investment balance would reach if it earned one steady rate. Enter what you have now, what you add each month, a rate, a number of years (up to 100) and how often interest compounds: annually, quarterly, monthly or daily. The result splits the future balance into what you deposited and what the interest added, with a chart and a row for every year.

With the starting values of $1,000 plus $100 a month at 7% for 10 years, compounded annually, you deposit $13,000 and end with $19,072.32. Each deposit earns interest from the end of the month it is made, even with annual compounding, so a bank that credits a year's interest only on the balance held all year would pay a little less. Set the monthly contribution to 0 to follow a single lump sum.

FV = P × (1 + i)^m + PMT × ((1 + i)^m − 1) ÷ i

i = (1 + r ÷ n)^(n ÷ 12) − 1

P is the starting balance, PMT the deposit made at the end of each month, r the annual rate as a decimal, n the number of times interest compounds in a year and m the number of months. i is the monthly rate that grows the balance exactly as fast as compounding n times a year. For a lump sum with no deposits this reduces to the textbook A = P × (1 + r ÷ n)^(n × t).

Example: $10,000 at 6% for 10 years with no deposits grows to $17,908.48 compounded annually, $18,193.97 monthly and $18,220.29 daily.

The rate is the same every year and the deposit never changes. Nothing is taken off for taxes, fees or inflation. Investment returns vary from year to year, so the result is an illustration at the rate you chose, not a forecast.