Compound Interest Calculator
See how your savings or investments grow over time with compound interest. Add monthly contributions to model regular investing.
Investment Details
Final Balance
$144,573
Total Contributed
$58,000
Interest Earned
$86,573
Where your balance comes from
Balance Growth Over Time
Notice how interest (green) grows faster than contributions over time — this is compound growth
Year-by-Year Growth
20 years| Year | Balance | Contributed | Interest | Interest % |
|---|---|---|---|---|
| Year 1 | $13,201 | $12,400 | $801 | 6.1% |
| Year 2 | $16,634 | $14,800 | $1,834 | 11.0% |
| Year 3 | $20,315 | $17,200 | $3,115 | 15.3% |
| Year 4 | $24,262 | $19,600 | $4,662 | 19.2% |
| Year 5 | $28,495 | $22,000 | $6,495 | 22.8% |
| Year 6 | $33,033 | $24,400 | $8,633 | 26.1% |
| Year 7 | $37,900 | $26,800 | $11,100 | 29.3% |
| Year 8 | $43,118 | $29,200 | $13,918 | 32.3% |
| Year 9 | $48,714 | $31,600 | $17,114 | 35.1% |
| Year 10 | $54,714 | $34,000 | $20,714 | 37.9% |
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Sign in →How Compound Interest Works
Compound interest means you earn interest not just on your initial investment, but also on all the interest you have already earned. Over time, this creates an exponential growth effect — often called the "snowball effect."
Compounding frequency matters. Daily compounding yields slightly more than monthly, which yields more than annually, because interest is applied — and starts earning its own interest — more often. For most savings accounts and investments, monthly compounding is the standard.
Compound Interest Formula
A = P(1 + r/n)^(nt) + PMT × [((1 + r/n)^(nt) − 1) / (r/n)]Where P = principal, r = annual rate, n = compounding periods/year, t = years, PMT = monthly contribution
Time is your most powerful lever. Starting 10 years earlier can double your final balance, even with no extra contributions. A common rule of thumb is the Rule of 72: divide 72 by your annual rate to estimate how many years it takes to double your money. At 7%, your money doubles roughly every 10 years.