Compound interest calculator
Calculator
The calculator needs JavaScript. The tables below give the same numbers for common cases.
How it is worked out
- Rate per month (from monthly compounding) i = (1 + r ÷ n)^(n ÷ 12) − 1 = 0.00416667.
- Future value = P × (1 + i)^m + C × ((1 + i)^m − 1) ÷ i with m = 120 months.
- Monthly deposits are added at the end of each month.
- Result: $16,470.09.
| Inputs | Answer |
|---|---|
| Starting amount: 10000; Annual interest rate: 5; Compounded: Monthly; Years: 10; Monthly deposit: 0 | $10,000.00 at 5% for 10 years grows to $16,470.09, of which $6,470.09 is interest. |
| Starting amount: 10000; Annual interest rate: 5; Compounded: Monthly; Years: 10; Monthly deposit: 100 | $10,000.00 plus $100.00 a month at 5% for 10 years grows to $31,998.32, of which $9,998.32 is interest. |
| Starting amount: 2500; Annual interest rate: 3; Compounded: Daily; Years: 20; Monthly deposit: 50 | $2,500.00 plus $50.00 a month at 3% for 20 years grows to $20,976.79, of which $6,476.79 is interest. |
How to use it
With compound interest each period's interest is added to the balance and earns interest in the next period. $10,000 at 5% compounded monthly for 10 years grows to about $16,470; adding $100 a month raises it to about $31,998.
The calculator converts your compounding frequency into a monthly rate, then applies the standard future-value formulas with deposits at the end of each month. The effective annual rate is shown too. These are estimates from the numbers you type, not financial advice or an offer; real products add fees and change rates.
Frequently asked questions
What is the compound interest formula?
A = P × (1 + r ÷ n)^(n × t), with n compounding periods a year.
Does more frequent compounding matter?
Slightly: 5% compounded daily is a little more than 5% compounded yearly, but the rate and the time matter far more.
When are the deposits made?
At the end of each month.
Method: standard arithmetic shown step by step; no outside data is used. Checked 2026-11-12.
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General information only. Results are plain arithmetic on the numbers you enter; check anything important (money, health, school work) against your own records or the official source.