Auto Loan Calculator

An auto loan's monthly payment depends on more than the sticker price and interest rate alone — the actual amount financed is a genuinely different number once down payment, trade-in value, and sales tax are all factored in, which is exactly why a naive 'price times rate' mental model tends to understate the real numbers involved.

Sales tax is the piece most easily underestimated, partly because it's not always obvious how it interacts with a trade-in. Many jurisdictions tax only the net amount — the vehicle price minus the trade-in value — on the logic that the trade-in effectively functions as a partial payment rather than separate taxable income. This convention means a trade-in provides a genuine double benefit: it directly reduces the amount financed, and it often reduces the sales tax owed too, since the tax applies to a smaller taxable base. Not every jurisdiction follows this convention, though — some tax the full vehicle price regardless of trade-in — so checking your specific local rule before assuming the net-taxation convention applies is worth doing before finalizing a budget.

Once the actual amount financed is determined — price, minus down payment, minus trade-in, plus sales tax — the payment calculation itself uses the same standard amortization math that underlies any fixed-rate installment loan: a payment that stays constant every month, split between principal and interest in a ratio that shifts over the loan's term as the balance shrinks.

Term length involves a genuine tradeoff worth understanding rather than defaulting to whatever term produces the lowest monthly payment. A longer term — 6 or 7 years instead of a more traditional 4 or 5 — lowers the monthly payment, which can make a given budget stretch to a more expensive vehicle. But it also means paying interest for more months on a slower-shrinking balance, meaningfully increasing total interest paid over the loan's life, and can leave a borrower 'underwater' (owing more than the car is worth) for a longer stretch of the loan, since vehicles depreciate faster than a long-term loan's balance typically shrinks in the early years.

Comparing the total cost — amount financed plus total interest — across a few different term lengths and down payment scenarios, rather than fixating on the lowest monthly payment alone, is exactly the kind of comparison this calculator is built to make concrete rather than abstract.