Watch your money snowball
With compound interest, the interest you earn is added to your balance and starts earning interest too. Enter a starting balance, interest rate, time and compounding frequency — daily and monthly are typical for high-yield savings accounts, CDs and money market accounts — to see the final balance, total interest and the APY (annual percentage yield).
Add a monthly deposit to model regular saving, such as an emergency fund or a college fund. A year-by-year table shows your contributions, interest and balance, and the result is compared with simple interest so you can see exactly what compounding adds.
How to calculate compound interest
- 1
Enter your starting balance
A lump sum or your current savings.
- 2
Set the rate and time
Annual interest rate (APR) and number of years.
- 3
Choose the compounding frequency
Daily, monthly, quarterly, semi-annually or yearly.
- 4
Add monthly deposits (optional)
To model regular saving.
Key features
Five compounding options
From daily to yearly.
Monthly contributions
Model a savings plan, not just a lump sum.
APY
The true yearly return after compounding.
Growth table
Balance for every year.
Common uses
- High-yield savings: Estimate how an emergency fund grows.
- CDs: Project the value of a certificate of deposit at maturity.
- Saving goals: See how long it takes to reach a target.
$10,000 at 5% compounded monthly
| After | Balance | Interest earned |
|---|---|---|
| 5 years | $12,834 | $2,834 |
| 10 years | $16,470 | $6,470 |
| 20 years | $27,126 | $17,126 |
| 30 years | $44,677 | $34,677 |
Growth accelerates over time: the last 10 years earn more interest than the first 20 combined.
Tips and good to know
- Compare savings accounts by APY, not APR: 5% compounded monthly is a 5.116% APY.
- Interest earned in a regular savings account is taxable; the results here are before tax.
- Investing in stocks or funds instead? Use the Investment Calculator.