Compound Interest Calculator
Simulate the growth of your money with the compound interest formula. Add monthly contributions and see how time and rate impact your wealth.
Final balance
$2,295.23
Total invested
$2,200.00
Interest earned
$95.23
| Period | Invested | Interest | Total |
|---|---|---|---|
| 1 month | $1,100.00 | $5.00 | $1,105.00 |
| 2 months | $1,200.00 | $10.52 | $1,210.52 |
| 3 months | $1,300.00 | $16.58 | $1,316.58 |
| 4 months | $1,400.00 | $23.16 | $1,423.16 |
| 5 months | $1,500.00 | $30.28 | $1,530.28 |
| 6 months | $1,600.00 | $37.93 | $1,637.93 |
| 7 months | $1,700.00 | $46.12 | $1,746.12 |
| 8 months | $1,800.00 | $54.85 | $1,854.85 |
| 9 months | $1,900.00 | $64.12 | $1,964.12 |
| 10 months | $2,000.00 | $73.94 | $2,073.94 |
| 11 months | $2,100.00 | $84.31 | $2,184.31 |
| 12 months | $2,200.00 | $95.23 | $2,295.23 |
What is Compound Interest Calculator?
In compound interest, each period's interest itself starts earning interest along with the principal — the famous "interest on interest". It models nearly every investment (savings, CDs, Treasuries) and most loans. The formula: A = P × (1 + r)ⁿ. Small rates over long periods produce explosive growth.
How to use
- Enter the initial capital (your principal).
- Set the interest rate and period.
- Add monthly contributions if any.
- See the final amount, total invested and interest earned.
How it works
- 1Enter the initial principal you already have to invest
- 2Add a monthly contribution (the amount you plan to invest every month)
- 3Set the monthly interest rate (e.g. 0.5% per month ≈ 6.17% per year)
- 4Pick a period in months or years and see the result
Frequently asked questions
What is the difference between simple and compound interest?
With simple interest, interest is always calculated on the original principal. With compound interest, the interest from each period is added to the principal — generating "interest on interest" over time.
How do I convert an annual rate to monthly?
Use: monthly rate = (1 + annual rate)^(1/12) − 1. Example: 12% per year ≈ 0.949% per month.
Do monthly contributions really make a difference?
Yes. Regular monthly contributions have a huge impact in the long run. Often they contribute more to the final balance than the initial principal does.
How accurate is this calculator?
The math is exact for the rate and contributions you enter. It does not account for taxes, inflation or fees — adjust the rate accordingly to model net returns.
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