How Fixed-Rate Loan Amortization Works
Loan amortization is the scheduled repayment of debt principal and accrued interest through regular periodic installments over a defined time horizon. Each payment is divided into an interest portion (the cost of borrowing against the current outstanding balance) and a principal portion (equity repayment that reduces the debt).
Equal Payment (Annuity) vs. Equal Principal (Linear)
- Equal-Payment Amortization (Fixed Monthly Installment): The borrower pays a constant dollar amount every month. In early periods, interest comprises the bulk of the payment; over time, as the remaining balance declines, interest drops and principal repayment accelerates until the loan reaches a zero balance.
- Equal-Principal Amortization (Decreasing Monthly Installment): The borrower pays a fixed amount of principal each month plus whatever monthly interest has accrued on the remaining balance. Installments start higher and decrease steadily, resulting in faster principal reduction and lower total interest paid over the life of the loan.
Mathematical Formulas
P_periodic = L * [ r * (1 + r)^n ] / [ (1 + r)^n - 1 ]
- L = Initial loan principal balance
- r = Periodic monthly interest rate (Annual Rate / 12)
- n = Total number of monthly installments (Term in Years × 12)
Benefits of Additional Principal Payments
Making recurring additional principal payments directly reduces the outstanding debt ahead of schedule. Because interest is computed on the remaining principal balance, extra payments compound into significant cumulative interest savings and substantially shorten the time to debt-free ownership.
Frequently Asked Questions
- Qual a diferença entre Tabela Price e Tabela SAC?
- Na Tabela Price (parcela fixa), as prestações mensais são constantes ao longo do tempo. Na Tabela SAC (amortização constante), o valor amortizado da dívida é igual todo mês, fazendo com que as parcelas comecem mais altas e diminuam mês a mês, resultando em menor custo total de juros.
- Como a amortização extraordinária mensal reduz o financiamento?
- Pagamentos extras ao mês abatem diretamente o principal da dívida antes do prazo contratado. Como os juros são calculados sobre o saldo devedor restante, abater o saldo antecipadamente reduz expressivamente o total de juros e encurta os anos de pagamento.
- Alterar a moeda afeta o cálculo do empréstimo?
- Não. A seleção de moeda altera exclusivamente os símbolos visuais e a formatação numérica de acordo com o padrão local, sem aplicar nenhuma taxa de câmbio aos valores.