Calculadora de Juros Simples
- Created by
- Renato Passos, Eng. de Software
- Reviewed by
- Renato Passos, Eng. de Software
Last updated: Apr 18, 2026
Formula
J = P · i · n ; M = P · (1 + i · n)
About this calculator
The Simple Interest Calculator is a practical tool for calculating interest and final amount in financial operations using simple interest capitalization. The calculation is based on the formula J = P × i × n, where P is the principal, i is the interest rate per period, and n is the number of periods. The final amount M is given by M = P × (1 + i × n). Simply enter the principal, interest rate, and time to get instant results.
This calculator is useful in situations such as personal loans, short-term financing, fixed-income investments with simple interest, and calculation of late fees or penalties. For example, when lending money to a friend at an agreed rate, you can quickly determine how much you will receive back. It is also applicable in discount operations for invoices or securities where interest is calculated linearly.
Important precautions: ensure that the interest rate and period are in the same time unit (months, years, etc.). If the rate is annual and the period is in months, convert the rate to monthly or the period to years. Remember that simple interest does not consider compounding, differing from compound interest. This tool does not replace professional financial advice; use it as support for estimates.
Frequently asked questions
What is the difference between simple interest and compound interest?
In simple interest, interest is calculated only on the principal, without adding previous interest. In compound interest, interest is calculated on the accumulated amount, generating 'interest on interest'.
Can I use this calculator to calculate late payment interest?
Yes, as long as the late payment interest rate is fixed and applied linearly. Just enter the debt amount, the interest rate, and the delay period.
How should I enter the interest rate?
Enter the percentage rate without the percent symbol. For example, for 5% per month, enter 5. The calculator automatically converts it to decimal.
What if the rate and period are in different units?
Convert one of them to the same unit. For example, if the rate is annual and the period in months, divide the rate by 12 to get the monthly rate.
Is this calculator suitable for investments?
Yes, for investments that pay simple interest, such as some short-term fixed-income securities. Check the terms of your investment.