What is an auto loan calculator?
An auto loan calculator works out your monthly car payment from the numbers that actually determine it — not just the sticker price.
It adds sales tax (calculated after your trade-in credit, as most US states do) and dealer fees, subtracts your down payment and trade-in, then amortizes the remainder across your term at your APR. The result is both a monthly payment and the total cost of the car once interest is included.
Its main use is checking a dealer's quote before you sign, and seeing what a longer term genuinely costs — a lower payment across more months is not a discount.
How the payment is worked out
The sticker price is rarely what you finance. Tax and fees get rolled in; your down payment and trade-in come off.
Tax is added
Sales tax is calculated on the price after your trade-in is deducted, which is how most US states handle it — a real saving if you're trading in.
Cash comes off
Your down payment and trade-in reduce the amount financed. Fees get added back on, since dealers usually roll them into the loan.
The rest is amortized
What's left is spread across your term at your APR. A longer term lowers the payment but raises total interest — often by a lot.
Why loan term matters more than you'd think
Stretching a loan is the easiest way for a dealer to hit a monthly payment you asked for. It's also the most expensive.
A $28,000 amount financed at 6.9% APR:
The lower payment feels better every month. Over the life of the loan it costs thousands more — and you spend far longer owing more than the car is worth.
Negotiate the price of the car, not the monthly payment. Any payment can be reached by extending the term — that's not a discount, it's a longer bill.
Things this doesn't include
Insurance
Often $100–$250 a month, and it isn't part of your loan payment. Newer and more powerful cars cost more to insure, sometimes dramatically. Worth getting a quote before committing.
Depreciation
New cars typically lose a large share of their value in the first few years. That doesn't affect your payment, but it's why long loans leave people "underwater" — owing more than the car would sell for.
Fuel, maintenance, and repairs
None of it appears here. A rough planning figure is a few hundred dollars a month once you include fuel, servicing, and tyres.
Manufacturer promotional rates
0% APR offers exist but usually replace a cash rebate. Compare the total cost of "0% financing" against "rebate plus a credit union loan" — the second is often cheaper.
Common questions
The things people usually want to know before trusting a number like this.
Is the sales tax calculated before or after my trade-in?
This calculator applies tax after the trade-in is deducted, which is how the majority of US states handle it — you're only taxed on the difference. A minority of states tax the full purchase price regardless. Check your state's rule, because on a large trade-in the difference can be over a thousand dollars.
Should I take the longest term to lower my payment?
Generally no. Longer terms mean more total interest and a longer period owing more than the car is worth. A common guideline is to keep auto loans to 60 months or less; if you can only afford a car at 84 months, that's usually a signal the car is too expensive rather than that the term should be longer.
Does a bigger down payment help much?
Yes, in three ways: it reduces the amount financed, it reduces total interest, and it lowers the risk of going underwater. Many lenders also offer better rates above certain down payment thresholds. Around 20% is a common target for a new car, though it isn't a hard rule.
Why is my dealer's quoted payment different?
Usually because of items this calculator doesn't ask about: extended warranties, gap insurance, paint protection, documentation fees, or a different term than you assumed. Ask for the out-the-door price and the exact term in writing, then re-run those numbers here.
Can I pay this loan off early?
Most auto loans use simple interest, so extra payments toward principal reduce your total interest. Some subprime loans use precomputed interest where the total is fixed at signing — in that case paying early saves little. Your loan agreement will say which applies.
Related calculators
Other tools that pair well with this one.