Compound interest calculator
Enter the starting amount, the interest rate and the term to see the final amount and how much it earned with interest on interest.
Free · no sign-up The values you type stay in your browser: nothing is sent or stored.
Final amount
R$11,268.25
- Starting amount
- R$10,000.00
- Total interest
- R$1,268.25
Your result in words
Investing R$10,000.00 at 1% per month for 12 months, you will have R$11,268.25, and R$1,268.25 of that is interest.
Growth chart
| Total with interest | Starting amount | |
|---|---|---|
| 1 | R$10,100.00 | R$10,000.00 |
| 2 | R$10,201.00 | R$10,000.00 |
| 3 | R$10,303.01 | R$10,000.00 |
| 4 | R$10,406.04 | R$10,000.00 |
| 5 | R$10,510.10 | R$10,000.00 |
| 6 | R$10,615.20 | R$10,000.00 |
| 7 | R$10,721.35 | R$10,000.00 |
| 8 | R$10,828.57 | R$10,000.00 |
| 9 | R$10,936.85 | R$10,000.00 |
| 10 | R$11,046.22 | R$10,000.00 |
| 11 | R$11,156.68 | R$10,000.00 |
| 12 | R$11,268.25 | R$10,000.00 |
Informational estimate, without fees or inflation. Check taxes and charges for your case; the real result may differ.
How it works
What is compound interest
With compound interest, the interest of each period is added to the amount and starts earning interest too, the famous interest on interest. That is why growth speeds up over time, and it is how investments, credit cards and overdrafts work.
A tip for investing
Time matters more than the amount: the sooner you start, the more the interest works for you. Always compare rates in the same unit, monthly with monthly and yearly with yearly.
Formula
How to calculate
M is the final amount, P the initial value, i the rate per period (1% = 0.01), n the number of periods and J the interest. With an annual rate, the calculator uses the equivalent monthly rate (i with subscript m, computed from the annual one, subscript a) and applies it to the term in months.
Example
With round numbers, so you can check the math:
Investing R$10,000.00 at 1% per month for 12 months, you will have R$11,268.25, and R$1,268.25 of that is interest.
Frequently asked questions
What is the difference between simple and compound interest?
With simple interest, the rate always applies to the starting amount. With compound interest, it applies to the amount already increased by interest, so growth is bigger over time.
How do I convert a monthly rate to a yearly one?
Raise 1 plus the monthly rate to the power of 12 and subtract 1. For example, 1% per month is about 12.68% per year, not 12%.
Does the calculator deduct tax or fees?
No. The result is gross, without income tax, transaction tax or broker fees. For real investments, deduct those items.
Math checked by the JuntaTudo team · updated on Nov 12, 2026
