Compound interest calculator
Compound interest is interest earned on interest: each period's growth joins the balance, so the next period grows from a bigger total. The longer money stays in, the more of the final balance is growth rather than deposits. This calculator shows that split, year by year.
Compounding
Balance after 20 years
$144,573
Deposits$58,000Interest$86,573 (60%)
Year by year
| Year | Deposits | Interest | Balance |
|---|---|---|---|
| 1 | $12,400 | $801 | $13,201 |
| 2 | $14,800 | $1,834 | $16,634 |
| 3 | $17,200 | $3,115 | $20,315 |
| 4 | $19,600 | $4,662 | $24,262 |
| 5 | $22,000 | $6,495 | $28,495 |
| 6 | $24,400 | $8,633 | $33,033 |
| 7 | $26,800 | $11,100 | $37,900 |
| 8 | $29,200 | $13,918 | $43,118 |
| 9 | $31,600 | $17,114 | $48,714 |
| 10 | $34,000 | $20,714 | $54,714 |
| 11 | $36,400 | $24,747 | $61,147 |
| 12 | $38,800 | $29,246 | $68,046 |
| 13 | $41,200 | $34,244 | $75,444 |
| 14 | $43,600 | $39,776 | $83,376 |
| 15 | $46,000 | $45,882 | $91,882 |
| 16 | $48,400 | $52,603 | $101,003 |
| 17 | $50,800 | $59,983 | $110,783 |
| 18 | $53,200 | $68,070 | $121,270 |
| 19 | $55,600 | $76,915 | $132,515 |
| 20 | $58,000 | $86,573 | $144,573 |
Two savers
Ana and Ben each put $200 a month into the same fund, earning 7% a year. Ana starts at 25 and stops at 35. Ben starts at 35 and keeps going until 65. Who has more at 65?
Worked example
You put $10,000 in an account paying 7% a year, compounded monthly, and add $200 at the end of every month for 20 years.
- Deposits: $10,000 + $200 × 240 months = $58,000.
- Each month's interest is added to the balance, so the next month's interest is paid on it too.
- After 20 years the balance is $144,573.
$86,573 of that (60%) is interest, not money you put in.
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