Calculadora de Dívida com Cartão
- Created by
- Renato Passos, Eng. de Software
- Reviewed by
- Renato Passos, Eng. de Software
Last updated: Apr 18, 2026
Formula
meses = log(PMT / (PMT − D·r)) / log(1+r)
About this calculator
This calculator helps you simulate the minimum payment of your credit card bill. It shows how many months it will take to pay off your debt and the total interest paid, considering the revolving credit interest rate. Simply enter the total debt amount, the minimum monthly payment (usually 15% of the total), and the card's monthly interest rate.
The calculation uses a logarithm formula to determine the number of months needed to zero the balance, assuming you always pay the same minimum amount. The formula is months = log(PMT / (PMT − D·r)) / log(1+r), where PMT is the minimum payment, D is the total debt, and r is the monthly interest rate. The result shows the total time and the interest cost.
Use this tool when planning to pay off a credit card debt by making only minimum payments. For example, if you have a $2,000 bill, pay $300 per month, and the bank charges 12% per month, the calculator shows it will take 8 months and cost $400 in interest. This helps understand the true cost of revolving credit.
Important precautions: credit card interest rates in Brazil are among the highest, often above 10% per month. Paying only the minimum can prolong the debt for many months and multiply the amount owed. Whenever possible, negotiate installment plans with lower interest rates or use this calculator to compare scenarios and make more informed financial decisions.
Frequently asked questions
What is the minimum payment on a credit card?
It is the minimum amount you must pay to avoid late fees, usually around 15% of the total bill. The remainder goes into revolving credit, subject to high interest.
How does the calculator determine the number of months?
It uses a mathematical formula that considers the debt amount, minimum payment, and interest rate. The result shows how many months it will take to pay off the debt by always paying the same minimum amount.
Are credit card interest rates really that high?
Yes, in Brazil the revolving credit interest rate can exceed 300% per year. Paying only the minimum can cause the debt to grow quickly.
Can I use this calculator for installment plans?
No, it is designed only for minimum payments on revolving credit. For installment plans, look for a fixed-interest installment calculator.
What does the total interest amount mean?
It is the sum of all interest you will pay over the period until the debt is cleared, considering the monthly minimum payment.