Compound Interest Calculator
Enter a starting amount, an interest rate and a number of years to see what your money grows to when interest earns interest. Switch the compounding frequency to see how much difference it makes.
Compound Interest
Growth with yearly, monthly or daily compounding
How it works
- Formula: A = P × (1 + r/n)^(n × t).
- More frequent compounding gives a slightly higher effective yearly rate.
- Time matters most: doubling the years more than doubles the interest.
- The rule of 72: divide 72 by the rate to estimate the years to double.
Worked example: 10,000 at 6% for 10 years, monthly
- 1Monthly rate: 6% ÷ 12 = 0.5%.
- 2Periods: 10 × 12 = 120.
- 310,000 × 1.005^120 ≈ 18,194.
≈ 18,194 — of which 8,194 is interest
Growth of 10,000 at 6% by compounding frequency (10 years)
| Compounding | Final amount | Effective rate |
|---|---|---|
| Yearly | 17,908 | 6.000% |
| Quarterly | 18,140 | 6.136% |
| Monthly | 18,194 | 6.168% |
| Daily | 18,220 | 6.183% |
Frequently asked questions
What is compound interest?
Interest calculated on the original amount plus all interest already added, so your balance grows faster every period.
How long does it take to double my money?
Roughly 72 divided by the interest rate. At 6% that is about 12 years; at 8% about 9 years.
Is daily compounding much better than monthly?
Only slightly. At 6% the difference is about 0.015 percentage points a year.
Does this include monthly deposits?
No — for regular deposits use the Savings Growth or Retirement Savings calculator.
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