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Compound interest calculator
Growth of $1,000.00 initial + $100.00/month at 7%/yr
| Years | Invested | Interest | Total |
|---|---|---|---|
| 1 | $2,200.00 | $108.03 | $2,308.03 |
| 2 | $3,400.00 | $307.62 | $3,707.62 |
| 3 | $4,600.00 | $605.18 | $5,205.18 |
| 5 | $7,000.00 | $1,522.14 | $8,522.14 |
| 10 | $13,000.00 | $6,072.32 | $19,072.32 |
| 15 | $19,000.00 | $14,869.51 | $33,869.51 |
| 20 | $25,000.00 | $29,623.32 | $54,623.32 |
Formula
A = P·(1+i)n + D·[((1+i)n − 1) / i]
Worked example: $5,000.00 initial with $200.00/month for 10 years at 7%/yr (i = 0.565%/month compound-equivalent) grows to $44,046.10, of which $15,046.10 is pure interest.
How to read the result
Compound interest is earned on the principal and on previously accumulated interest, which is why growth accelerates over time. Rates here are annual (APY-style) converted to the compound-equivalent monthly rate, the convention used by savings accounts, CDs and index funds. Note that this simulation does not deduct taxes (interest is generally taxable as income in the US) or fund fees.
Over long horizons the monthly contribution usually matters more than the rate: doubling your deposit is immediate and guaranteed, doubling the return depends on the market. Use the table above to compare horizons.
Last updated: · Methodology and sources