How Installment Loans Amortize
When you borrow money through an installment loan—such as an auto loan, personal loan, or student loan—the lender computes your fixed periodic payment using an amortization formula:
Each month, your interest charge equals Current Balance × (Annual Rate ÷ 12). The remainder of your payment reduces principal.
The Pitfall of Long Loan Terms
Lenders frequently market longer loan terms (such as 72 or 84 months for auto loans) to advertise attractive, lower monthly payments. However, stretching out payments exponentially inflates total borrowing costs:
Financing a $25,000 loan at 8.0% interest:
- 36 Months (3 yrs): Monthly payment is $783. Total interest paid is $3,205.
- 72 Months (6 yrs): Monthly payment drops to $438, but total interest jumps to $6,547 (more than double!).
Frequently Asked Questions
An origination fee is an upfront processing charge (typically 1% to 8%) deducted from your loan disbursement or added to your balance when the loan closes.
Most consumer personal and auto loans in the US do not have prepayment penalties, but you should always check your loan agreement before making extra principal payments.