Simple interest calculator
Enter the amount, the rate and the term to see the interest and the final amount, with the rate always applied to the starting amount.
Free · no sign-up The values you type stay in your browser: nothing is sent or stored.
Final amount
R$11,200.00
- Starting amount
- R$10,000.00
- Total interest
- R$1,200.00
Your result in words
Applying 1% per month on R$10,000.00 for 12 months, the interest is R$1,200.00 and the final amount is R$11,200.00.
Growth chart
| Total with interest | Starting amount | |
|---|---|---|
| 1 | R$10,100.00 | R$10,000.00 |
| 2 | R$10,200.00 | R$10,000.00 |
| 3 | R$10,300.00 | R$10,000.00 |
| 4 | R$10,400.00 | R$10,000.00 |
| 5 | R$10,500.00 | R$10,000.00 |
| 6 | R$10,600.00 | R$10,000.00 |
| 7 | R$10,700.00 | R$10,000.00 |
| 8 | R$10,800.00 | R$10,000.00 |
| 9 | R$10,900.00 | R$10,000.00 |
| 10 | R$11,000.00 | R$10,000.00 |
| 11 | R$11,100.00 | R$10,000.00 |
| 12 | R$11,200.00 | 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 simple interest
With simple interest the rate always applies to the starting amount, not to the interest already accumulated. Earnings grow in a straight line: the same amount every period.
Where it shows up
Simple interest is common in invoice discounting, late fees and some bonds. In most investments and loans, compound interest is what applies.
Formula
How to calculate
J is the interest, P the initial value, i the rate per period (1% = 0.01), n the number of periods and M the final amount. With an annual rate and a term in months, the rate is proportional: 12% a year equals 1% a month.
Example
With round numbers, so you can check the math:
Applying 1% per month on R$10,000.00 for 12 months, the interest is R$1,200.00 and the final amount is R$11,200.00.
Frequently asked questions
When should I use simple interest?
When the rate applies only to the original amount, as in some discounts and late fees. In investments and loans, compound interest is the norm.
Does simple interest earn less than compound?
For terms longer than one period, yes: compound earns more because interest also earns interest. In the first period both give the same result.
Do a yearly rate and a term in months work together?
Yes. The calculator divides the yearly rate by 12 to get the proportional monthly rate and multiplies it by the number of months.
Math checked by the JuntaTudo team · updated on Nov 12, 2026
