Free Compound Interest Calculator
This compound interest calculator shows how your savings grow when interest earns interest, with an optional monthly deposit.
Compound interest calculator examples: $10,000 plus $200 a month
| Rate | 10 years | 20 years | 30 years |
|---|---|---|---|
| 3% a year | $41,442 | $83,868 | $141,116 |
| 5% a year | $47,527 | $109,333 | $211,129 |
| 7% a year | $54,714 | $144,573 | $325,159 |
| 9% a year | $63,216 | $193,669 | $513,454 |
Why time matters more than the rate
Doubling the time more than doubles the interest, because each year's interest earns interest in every year that follows. Starting earlier with smaller deposits often beats starting later with bigger ones.
Frequently asked questions
How does this compound interest calculator work?
Each month, interest is added to your balance at the rate and compounding frequency you choose, then your monthly deposit is added. Over time you earn interest on your interest, which is why the balance curves upward.
What is the formula for compound interest?
For a single deposit: A = P × (1 + r/n)^(n×t), where P is the starting amount, r the yearly rate, n the number of compounding periods a year and t the number of years. Regular deposits are added month by month.
Is interest on savings taxed in Australia?
Yes. Interest from bank accounts is assessable income and taxed at your marginal rate. Earnings inside super are taxed at up to 15%. This calculator shows returns before tax.
How much will $10,000 grow in 10 years?
At 5% a year compounded monthly, $10,000 grows to about $16,470 in 10 years with no extra deposits. Change the rate and years in the compound interest calculator to see your own result.