Auto Loan Calculator: Understand Your Car Payment Before You Buy

Dealers are skilled at manipulating the monthly payment number. A 72-month loan at 5% on a $35,000 car shows a payment of $563/month — lower than a 48-month loan at $806/month. But the 72-month loan costs $5,558 in total interest vs. $2,898 for the 48-month loan. You pay $2,660 more just to lower your monthly bill.

The longer the loan term, the more interest you pay — and the faster you go underwater (owing more than the car is worth). New cars depreciate roughly 20% in the first year and 50% over five years. A 72-month loan means you're likely upside-down for most of the loan term.

Always calculate total cost, not just monthly payment. Enter different loan terms in our auto loan calculator and look at the total interest column. That number, not the monthly payment, is what the loan actually costs you.

Many dealers make significant profit on financing by marking up the rate from what the lender actually charges. If a bank offers you 5% and the dealer gets you approved at 7% and presents it as 9%, the dealership pockets the difference without disclosing it.

The best approach: get pre-approved by your bank or credit union before going to the dealership. Come in with a loan offer in hand. The dealer may try to beat it — they often can, since they have lending relationships — but you now have a baseline and the dealer knows it.

Credit unions typically offer the best auto loan rates. If you're not a member, joining one for a loan is often worth the effort. Credit union auto loan rates consistently run 1–2% below commercial bank rates, saving hundreds to thousands on a typical loan.

A 20% down payment is the standard advice for auto loans. It reduces your loan principal, keeps you from going deeply underwater, and often qualifies you for better rates. On a $40,000 vehicle, $8,000 down means borrowing $32,000 — the difference in monthly payment and interest is substantial.

If you have negative equity on a trade-in (your trade is worth less than you owe), be cautious about rolling it into a new loan. This is how buyers end up financing $50,000+ on a $40,000 car, starting the new loan immediately underwater.

Our auto loan calculator lets you enter different down payment amounts and see the effect on payment and total cost. Run the numbers for 0%, 10%, and 20% down to see how much a larger down payment saves over the loan term.