Compound interest calculator
What your money becomes with a contribution every month. The rate starts at today's CDI (13.65% a year); change it as you like.
Data as of October 19, 2026, after the Central Bank release.
Compound interest calculator
- Final balance
- R$245,666.22
- Total invested
- R$121,000.00
- Interest earned
- R$124,666.22
In 10 years, R$1,000 to start and R$1,000 a month at 13.65% a year become R$245,666.22, of which R$124,666.22 is interest.
Gross figures: no income tax, IOF or fees. Monthly rate equivalent to the annual rate; contributions at the end of each month.
Year by year
| Year | Invested | Interest | Balance |
|---|---|---|---|
| 1 | R$13,000 | R$870 | R$13,870 |
| 2 | R$25,000 | R$3,497 | R$28,497 |
| 3 | R$37,000 | R$8,120 | R$45,120 |
| 4 | R$49,000 | R$15,012 | R$64,012 |
| 5 | R$61,000 | R$24,483 | R$85,483 |
| 6 | R$73,000 | R$36,885 | R$109,885 |
| 7 | R$85,000 | R$52,618 | R$137,618 |
| 8 | R$97,000 | R$72,136 | R$169,136 |
| 9 | R$109,000 | R$95,956 | R$204,956 |
| 10 | R$121,000 | R$124,666 | R$245,666 |
The math
Monthly rate = (1 + annual rate)^(1/12) − 1. Each month, balance = balance × (1 + monthly rate) + contribution.
Questions
What is compound interest?
Interest on interest: each month's return joins the balance and starts earning too. That's why the effect grows over time.
How much does R$ 1,000 a month become in 10 years at the CDI?
At today's CDI (13.65% a year), about R$242,071 before tax, of which R$122,071 is interest.