Compound interest calculator
Grow a starting amount and monthly deposits at any rate and compounding, with a year-by-year table.
- ๐บ๐ธ US federal & state rules
- See sources
Balance after 20 years
$125,510.22
$67,510.22 of that is interest
- Total deposits
- $58,000.00
- Total interest
- $67,510.22
- APY
- 6.168%
- Years to double (no deposits)
- 11.6
This is an example. Enter your numbers above and press the button to see your own result.
Balance by year
| Year 1 | $13,084 (deposits $12,400, interest $684) |
|---|---|
| Year 2 | $16,358 (deposits $14,800, interest $1,558) |
| Year 3 | $19,834 (deposits $17,200, interest $2,634) |
| Year 4 | $23,524 (deposits $19,600, interest $3,924) |
| Year 5 | $27,443 (deposits $22,000, interest $5,443) |
| Year 6 | $31,602 (deposits $24,400, interest $7,202) |
| Year 7 | $36,018 (deposits $26,800, interest $9,218) |
| Year 8 | $40,707 (deposits $29,200, interest $11,507) |
| Year 9 | $45,685 (deposits $31,600, interest $14,085) |
| Year 10 | $50,970 (deposits $34,000, interest $16,970) |
| Year 11 | $56,581 (deposits $36,400, interest $20,181) |
| Year 12 | $62,538 (deposits $38,800, interest $23,738) |
| Year 13 | $68,862 (deposits $41,200, interest $27,662) |
| Year 14 | $75,576 (deposits $43,600, interest $31,976) |
| Year 15 | $82,705 (deposits $46,000, interest $36,705) |
| Year 16 | $90,273 (deposits $48,400, interest $41,873) |
| Year 17 | $98,308 (deposits $50,800, interest $47,508) |
| Year 18 | $106,838 (deposits $53,200, interest $53,638) |
| Year 19 | $115,895 (deposits $55,600, interest $60,295) |
| Year 20 | $125,510 (deposits $58,000, interest $67,510) |
- Before taxes and fees. Interest in a regular taxable account is taxed each year, which lowers growth.
- A fixed rate is an assumption. Stock returns vary a lot from year to year.
Show the math
| Compounding | 6% compounded monthly (12 times a year) |
|---|---|
| APY | (1 + 6% รท 12)^12 - 1 = 6.1678% |
| Monthly growth rate | 0.5% |
| Deposits | $200.00 at the end of each month for 240 months |
What to do next
How it works
The yearly rate is first turned into a monthly growth rate that matches the compounding you pick: (1 + r/n)^(n/12) - 1. The balance then grows by that rate every month, and each monthly contribution is added at the start or end of the month.
The table shows the balance at the end of each year, split into what you put in and what the interest added.
Things to keep in mind
Taxes, fund fees and inflation are not included. A 1% yearly fee on a 20-year investment can take a large share of the gain, so it is worth trying a lower rate to see the effect.
Sources
- Investor.gov, compound interest calculator (SEC)Checked 2026-10-19
Frequently asked questions
How is compound interest calculated?
The balance grows by (1 + r/n) each period, where r is the yearly rate and n is the number of compounding periods. $10,000 at 5% compounded once a year for 10 years becomes $10,000 ร 1.05^10 = $16,288.95.
Does compounding frequency matter much?
A little. At 5%, yearly compounding gives a 5% APY, monthly gives 5.116% and daily gives 5.127%. The rate and the number of years matter far more.
What is the rule of 72?
Divide 72 by the yearly rate to estimate how many years it takes money to double. At 6% that is about 12 years, and the exact answer is 11.9.
Should I enter 10% for the stock market?
The rate is up to you. Many people use 5% to 7% for stocks after inflation, since past returns are not a promise of future ones.