How installment calculation works
The value of each installment depends on three factors: the total financed amount, the interest rate, and the number of installments. In general, interest is compounded (applied to the outstanding balance), and amortization is the portion of the payment that actually reduces the debt.
In the Price system, installments are equal: at the beginning, there are more interest charges and little amortization; over time, interest decreases and amortization increases. In SAC, amortization is constant, so installments start higher and gradually decrease month by month.
Rate conversion: be careful!
If your rate is annual (e.g., 18% per year), it must be converted to a monthly rate for the simulation. A common approximation is dividing by 12 (18% ÷ 12 = 1.5% per month). For more precision, use compound rate equivalence: (1 + 0.18)^(1/12) − 1.
Practical example (summary)
Financing R$50,000 in 24 installments at 1.5% per month: in the Price system, the payment remains constant; in SAC, the first installment is higher and decreases gradually. Although the total paid varies between systems, both use the same rate.
How to choose between SAC and Price
- Prefer starting with lower payments? → Price (fixed and predictable installment).
- Want to reduce the total interest over time? → SAC (decreasing installments).
- Need to prove income with a fixed payment? → Price is usually better.
- Planning to make early payments? → SAC tends to be more advantageous for amortization.
Tips to save money
- Negotiate the effective rate (monthly) and check the Total Effective Cost (CET).
- Simulate different terms: longer terms reduce the payment but increase total interest.
- Consider making extra amortizations when possible.
- Compare proposals from more than one institution.
Simulator limitations
This simulator uses standard formulas and does not include additional costs such as insurance, fees, taxes (IOF), or contractual variations. Always confirm the official conditions with your bank or financial institution.