Calculate Compound Interest
Compound interest earns interest on your interest. Enter a starting amount, rate, years and compounding frequency — and optionally a monthly deposit — to see how your money grows each year.
- Future value
- $31,998.32
- Total contributions
- $22,000.00
- Interest earned
- $9,998.32
- Effective annual yield (APY)
- 5.116%
Growth by year (10 rows)
| Year | Contributed | Interest | Balance |
|---|---|---|---|
| Year 1 | $11,200.00 | $539.50 | $11,739.50 |
| Year 2 | $12,400.00 | $1,168.01 | $13,568.01 |
| Year 3 | $13,600.00 | $1,890.06 | $15,490.06 |
| Year 4 | $14,800.00 | $2,710.44 | $17,510.44 |
| Year 5 | $16,000.00 | $3,634.20 | $19,634.20 |
| Year 6 | $17,200.00 | $4,666.60 | $21,866.60 |
| Year 7 | $18,400.00 | $5,813.23 | $24,213.23 |
| Year 8 | $19,600.00 | $7,079.91 | $26,679.91 |
| Year 9 | $20,800.00 | $8,472.79 | $29,272.79 |
| Year 10 | $22,000.00 | $9,998.32 | $31,998.32 |
Worked example
Example: $10,000 at 5% for 10 years, compounded annually
- A = 10,000 × (1 + 0.05)¹⁰
- 1.05¹⁰ = 1.62889
- A = $16,288.95
$16,288.95 — $6,288.95 of interest.
Formula
A = P × (1 + r/k)^(k·t)
With deposits: + C × ((1 + i)ⁿ − 1) ÷ i
k is the number of compounding periods per year; i is the equivalent monthly rate for monthly deposits. APY = (1 + r/k)ᵏ − 1.
Frequently asked questions
How do I calculate compound interest by hand?
Multiply the principal by (1 + rate per period) raised to the number of periods, then subtract the principal to get just the interest.
What is the Rule of 72?
Divide 72 by the interest rate to estimate the years to double your money. At 6%, about 12 years.
Does daily compounding make a big difference?
Only a little compared with monthly. At 5%, monthly gives 5.116% APY and daily 5.127%.
Last reviewed October 17, 2026 · Calculations run in your browser; nothing you enter is sent to a server.