How Auto Loan Payments Are Calculated
Auto loans use the same fixed-rate amortization formula as mortgages: M = P[r(1+r)^n] / [(1+r)^n - 1], where P is the amount financed (vehicle price minus down payment and trade-in), r is the monthly interest rate, and n is the total number of payments. Auto loans are typically short-term: 24, 36, 48, 60, or 72 months.
How Much Car Can You Afford?
A widely used guideline is the 20/4/10 rule: put at least 20% down, finance for no more than 4 years, and keep total vehicle costs (loan payment plus insurance) at or below 10% of your gross monthly income. Longer loan terms lower the monthly payment but significantly increase total interest and the risk of being "upside down" on the loan.
Total Cost of the Loan
On a $35,000 loan at 7% for 60 months, the monthly payment is approximately $693 and total interest is approximately $6,556. Extending the same loan to 72 months reduces the monthly payment to approximately $588 but increases total interest to approximately $7,354.
Frequently Asked Questions
Should I put more money down? A larger down payment reduces the amount financed, lowering both your monthly payment and total interest, and reduces the risk of negative equity in the first two years.
Can I pay off my auto loan early? Most auto loans allow early payoff without penalty. Even modest extra payments each month toward principal can significantly reduce total interest and shorten the loan term.