Updated October 2, 2026
Find the interest rate hidden in an instalment
You have the amount, the instalment and the term. The calculation returns the rate that makes the offer true.
Also searched as juros da parcela, reverse loan rate and hidden interest calculator.
Quick answer
A R$10,000 loan repaid in 24 instalments of R$560 has an implied rate of 2.51% a month, or 34.71% effective a year. At 2% a month the instalment would be R$528.71. The rate comes from inverting the Price formula and uses only the amount and instalments you enter.
Your result
Monthly effective rate
500.00%
- Annual effective rate
- 217,678,233,500.00%
- Rebuilt instalment
- R$50,000.00
How we got this number
If a desk quotes only instalment and term, the rate is implied. We invert the Price formula. A rate far above the private-sector payroll-loan average (3.79% a month in August 2026, per the Central Bank) usually means unsecured credit or hidden fees — take it to CET.
Formula and rules
Solve i from PMT = PV × i / [1 − (1+i)^−n]. Annual effective = (1+i)^12 − 1.
Examples
R$10,000, 24 × R$560
The implied rate is 2.51% a month (34.71% a year effective). At 2% a month the instalment would be R$528.71. Check it against the written contract.
Frequently asked questions
What if the instalment times term is below the principal?
That is not a positive-interest Price loan. Recheck the numbers you typed.
How do I find the interest rate of an instalment?
Enter the amount financed, the instalment and the number of months. The calculator finds the rate at which the present value of the instalments equals the amount financed. On R$10,000 repaid as 24 × R$560, the rate is 2.51% a month.
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Official sources used
Calculations run in your browser. We never ask for CPF, email or bank details, and values are not sent to our servers.
These tools provide educational estimates only. They are not a credit offer, financial advice, or an approval guarantee. Always check your payslip, contract and the current official rules.