Compound Interest Calculator
See how money could grow when interest earns interest. Enter a starting amount, a monthly contribution, a hypothetical annual rate, and a time frame.
Results
Estimated balance after 10 years
$17,175.24
- Total contributed
- $13,000.00
- Interest earned
- $4,175.24
| Year | Contributed | Interest | Balance |
|---|---|---|---|
| 1 | $2,200 | $79 | $2,279 |
| 2 | $3,400 | $224 | $3,624 |
| 3 | $4,600 | $437 | $5,037 |
| 4 | $5,800 | $722 | $6,522 |
| 5 | $7,000 | $1,084 | $8,084 |
| 6 | $8,200 | $1,525 | $9,725 |
| 7 | $9,400 | $2,051 | $11,451 |
| 8 | $10,600 | $2,665 | $13,265 |
| 9 | $11,800 | $3,371 | $15,171 |
| 10 | $13,000 | $4,175 | $17,175 |
Assumptions
- The rate is hypothetical. Returns are not guaranteed. Real investments go up and down, can lose money, and don't earn a fixed rate every year.
- The rate stays the same for the whole period.
- Contributions are made at the end of each compounding period. With monthly compounding that's once a month. With other frequencies, your monthly amount is converted to the same yearly total (for example, quarterly compounding adds 3 months of contributions each quarter).
- No taxes, fees, or inflation are included. Fund expense ratios, for example, would reduce the result.
- Amounts are rounded to the nearest cent.
How the calculation works
The calculator uses the standard future-value formula for a lump sum plus a series of regular contributions:
Where P is the initial investment, r is the annual rate as a decimal, n is the number of compounding periods per year, t is the number of years, and PMT is the contribution per period. When the rate is 0%, the result is simply the initial amount plus all contributions.
Reading the results
Total contributed is everything you put in. Interest earned is the growth on top of it. Over long periods the interest line can overtake contributions, which is the effect people mean when they talk about compounding. Try changing only the number of years to see how much time matters.