Compound interest calculator
See how a starting balance and regular deposits grow over time, and how much of the total is interest.
Balance after 20 years
$300,851
At 7% a year, $170,851 of it is interest.
- Initial deposit
- $10,000
- Monthly contributions
- $120,000
- Interest earned
- $170,851
- Final balance
- $300,851
Assumes a constant rate and deposits at the end of each month. Taxes, fees, and inflation are excluded.
How compound interest works
Compound interest is interest earned on both your deposits and the interest already added to your account.
An example
Start with $10,000, add $500 a month, and earn 7% a year compounded monthly. After 20 years, the estimated balance is $300,851. You deposited $130,000 and earned $170,851 in interest.
Change the rate, time, or monthly deposit to see how each affects the result. The chart separates deposits from interest, and the table shows your balance each year.
Which rate to enter
If your savings account quotes an APY, enter it and select Annually. APY already includes compounding. Choosing daily or monthly would count that compounding again.
The calculator converts your chosen rate and compounding frequency into a monthly growth rate. Your account may earn a different amount depending on deposit dates and when interest is added.
Common questions
Track your savings in Penny
Follow the balances in your savings and investment accounts.