Calculadora de Amortização
- Created by
- Renato Passos, Eng. de Software
- Reviewed by
- Renato Passos, Eng. de Software
Last updated: Apr 18, 2026
Formula
amort = P/n; juros_k = saldo_k × r
About this calculator
The Amortization Calculator from UtilizAí generates the complete table under the SAC (Constant Amortization System). You enter the loan amount, monthly interest rate, and number of installments. The calculator shows month by month: amortization (always equal), interest (decreasing), total payment, and outstanding balance. It's useful for simulating real estate financing, vehicle loans, or any credit with fixed amortization installments.
The calculation follows the SAC formula: amortization = total amount / number of installments. Interest each month is calculated on the remaining balance: interest = balance × monthly rate. Since amortization is constant, interest decreases each installment, so the total payment also falls over time. The outstanding balance decreases linearly to zero at the last installment.
Use this calculator to plan financing where you want to pay down the principal faster in the early months, reducing total interest cost. It's ideal for those who prefer decreasing payments over the contract term. Examples: home financing, car purchase, or working capital loans with decreasing cash flow.
Cautions: Ensure the interest rate entered is the effective monthly rate. SAC generates higher initial payments than the PRICE system, requiring greater payment capacity at the start. Check for additional fees (insurance, tariffs) to avoid distorting the true cost. The calculator considers only amortization and interest, no monetary correction.
Frequently asked questions
What is the difference between SAC and PRICE?
In SAC, amortization is constant and payments decrease; in PRICE, payments are fixed with increasing amortization. SAC results in lower total interest but higher initial payments.
Can I use it for real estate financing?
Yes, many banks use SAC for home financing. The calculator helps simulate installments and outstanding balance over time.
How do I calculate the monthly interest rate?
Divide the annual rate by 12. For example, 12% per year gives 1% (0.01) per month. Always use the effective rate, without compounding.
What is outstanding balance?
It is the amount still owed after each installment. In SAC, it decreases exactly by the constant amortization each month.
Does the calculator consider insurance or fees?
No. It calculates only amortization and interest. For the real cost, add administrative fees, insurance, and IOF to the total amount.