Compound interest calculator
What a starting amount and regular monthly additions grow to at a steady rate of return.
| Year | Contributed | Growth | Value |
|---|---|---|---|
| 1 | $16,000 | $919 | $16,919 |
| 2 | $22,000 | $2,339 | $24,339 |
| 3 | $28,000 | $4,294 | $32,294 |
| 4 | $34,000 | $6,825 | $40,825 |
| 5 | $40,000 | $9,973 | $49,973 |
| 10 | $70,000 | $36,639 | $106,639 |
| 15 | $100,000 | $86,971 | $186,971 |
| 20 | $130,000 | $170,851 | $300,851 |
| 25 | $160,000 | $302,290 | $462,290 |
| 30 | $190,000 | $501,150 | $691,150 |
How compounding works
Each month the balance earns a return, and next month's return is earned on that larger balance. Over long periods the growth on earlier growth becomes most of the total, which is why the years matter more than the rate at the start.
The formula
Each month: balance = balance × (1 + rate ÷ 12) + contribution. The table shows the totals at the end of each year.
Choosing a rate
Returns are never steady. US stocks have returned around 10% a year over the long run before inflation, with large swings; a lower rate gives a more cautious picture.
For education, not investment advice.
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