justyourcalculatorCompound Interest Calculator
Watch interest earn interest, or compare rates across compounding periods.
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Compound Interest Calculator
Grow a balance, or convert between compounding periods
Future balance
$31,998.32
after 10 years
- Initial investment
- $10,000.00
- Total deposits
- $12,000.00
- Interest earned
- $9,998.32
- Effective annual rate (APY)
- 5.116%
Deposits at the end of each month; interest compounded monthly. No taxes or fees.
- Starting amount$10,000
- Contributions$12,000
- Interest$9,998
- Starting amount
- Contributions
- Interest
How it was calculated
- APY = (1 + 0.05/12)^12 - 1 = 5.1162%
- Balance without deposits = $10,000.00 × (1 + APY)^10 = $16,470.09
| Year | Deposits | Interest | Ending balance |
|---|---|---|---|
| 1 | $1,200.00 | $539.50 | $11,739.50 |
| 2 | $1,200.00 | $628.50 | $13,568.01 |
| 3 | $1,200.00 | $722.05 | $15,490.06 |
| 4 | $1,200.00 | $820.39 | $17,510.44 |
| 5 | $1,200.00 | $923.75 | $19,634.20 |
| 6 | $1,200.00 | $1,032.41 | $21,866.60 |
| 7 | $1,200.00 | $1,146.62 | $24,213.23 |
| 8 | $1,200.00 | $1,266.68 | $26,679.91 |
| 9 | $1,200.00 | $1,392.88 | $29,272.79 |
| 10 | $1,200.00 | $1,525.54 | $31,998.32 |
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How the compound interest calculator works
Compound interest is interest on interest: each period's interest is added to the balance and earns interest itself. For a lump sum, the balance after t years is A = P(1 + r/n)^(nt), where r is the annual rate and n the number of compounding periods a year. Continuous compounding uses A = Pe^(rt).
The effective annual rate, or APY, puts different compounding periods on equal footing: 6% compounded monthly earns the same as 6.168% compounded once a year.
Using and checking your result
Published by JustYourCalculator. Check the units and assumptions above, and compare a known example before relying on the output. Calculations use browser arithmetic and may round displayed values.
This is an educational estimate, not a lender quote, tax filing calculation or investment recommendation. Actual costs depend on current rules, fees and your circumstances. Verify important decisions with official sources and a qualified adviser.
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