Loan calculator
Fixed instalment and constant amortisation side by side, with total interest.
Simulate a loan under the two most common Brazilian systems: fixed instalments (Price) and constant amortisation (SAC). Enter amount, monthly interest and term to see the instalment, total paid, total interest for each system and a chart of the falling balance.
How to use
- Enter the financed amount, the monthly interest rate and the term in months.
- Compare instalment and total interest under both systems, side by side.
- See in the chart how the outstanding balance falls in each system.
Fixed instalments (Price)
Every instalment is the same. What changes is the composition: early on, almost all of it is interest. The formula is PMT = PV × i ÷ (1 − (1 + i)^−n). Its advantage is predictability.
Constant amortisation (SAC)
Amortisation is constant and interest applies to a shrinking balance, so the first instalment is the highest and each one after is smaller. Total interest is always lower than with fixed instalments for the same term and rate.
Why the bank charges more than this simulation
A real contract adds mandatory insurance, admin fees, taxes and, in mortgages, inflation adjustment — usually 5% to 15% above the simulated instalment. Ask for the total effective cost before signing. If you are considering saving instead of borrowing, try the compound interest calculator.
Frequently asked questions
Which is better, fixed instalment or constant amortisation?
Constant amortisation pays less total interest because you amortise faster, but early instalments are much higher. Fixed instalments are easier to budget.
Why is the bank’s instalment higher than the simulation?
Because a real contract adds mandatory insurance, admin fees, taxes and, in mortgages, inflation adjustment. This simulation shows only interest on the outstanding balance.
How do I turn a yearly rate into a monthly one?
Not by dividing by 12. The correct conversion is compound: monthly = (1 + yearly)^(1/12) − 1.
Is early repayment worth it?
Almost always, and the earlier the better — at the start of a loan most of the instalment is interest.