About the compound interest calculator
Compound interest earns interest on previous interest. Over long periods, that snowball can become a large share of the final balance. Enter a starting amount, a monthly contribution, an assumed rate, and a time period to see the projected total and how much came from growth.
How to use this calculator
- Enter your starting amount and monthly contribution.
- Enter an assumed annual rate.
- Choose years and compounding frequency.
Worked examples
- 5% compounded yearly, no contributions
- 10,000 × 1.05¹⁰ = $16,288.95
About $16,289.
Measurement guidance
Choosing a rate
Savings accounts and bonds publish rates; investment returns vary. Try several rates to see a range of outcomes.
Frequently asked questions
What does compounding frequency change?
More frequent compounding slightly increases growth at the same annual rate.
When are contributions added?
At the end of each month.
Is growth guaranteed?
No. This is a projection using a constant rate.