Auto Loan Calculator — Monthly Car Payment & Total Interest

Inputs

Vehicle price ($)

Down payment ($)

Trade-in value ($)

Manufacturer rebate ($)

Cash incentive from the automaker. Lowers what you finance — but most states still charge sales tax on the price before the rebate.

State (optional)

Picks your state's average sales-tax rate and trade-in rule. You can still edit the rate below.

Sales tax (%)

Trade-in reduces sales tax

Most states tax only (price − trade-in). A few (CA, VA, MD, KY, HI, DC) tax the full price — uncheck for those. Auto-set when you pick a state.

Fees ($)

Doc, registration, and dealer fees rolled into the loan.

APR (%)

Loan term

Result

Adjust the inputs to see your result.

Recommended gear

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How the math works

A car loan is amortized: the amount you finance is spread across the term in equal monthly payments, each split between interest and principal. The calculator first figures the amount financed — vehicle price, minus your down payment, trade-in, and any manufacturer rebate, plus sales tax and fees. Then it applies the standard amortization formula using your monthly rate (APR ÷ 12) and the number of months.

In most states a trade-in lowers the taxable price, so it saves you sales tax on top of reducing the balance — this tool applies both effects. A manufacturer rebate is different: it lowers the amount you finance, but most states charge sales tax on the price before the rebate, so it doesn't cut your tax.

Why a longer term is a trap

Stretching a loan from 60 to 84 months drops the monthly payment, which feels like a win on the lot. But you pay interest for two extra years, and a car loses value far faster than the loan shrinks — so you spend most of those years underwater, owing more than the car is worth. Change the term above and watch the "total interest" line move.

Common mistakes

Shopping by monthly payment. Dealers can hit almost any payment by stretching the term. Negotiate the price and the APR, not the payment.
Taking dealer financing without comparing. Get pre-approved by your bank or credit union first — then make the dealer beat it.
Rolling negative equity forward. Financing what you still owe on an old car into the new loan stacks the underwater problem.
Ignoring total cost. Payment plus insurance plus fuel should stay under about 15% of take-home pay.

When this calculator is the wrong tool

This estimates a standard fixed-rate purchase loan. It doesn't model leases (different math entirely), balloon payments, variable-rate loans, or the tax specifics of every state. It's a planning tool, not financial advice — confirm the numbers with your lender.

Related guide

How Much Car Maintenance Really Costs (by Vehicle, Age & Mileage) What a car actually costs to keep on the road each year — by vehicle class, age, mileage, brand reliability, and your local labor market — with a low-high range and a monthly set-aside.

FAQ

Questions, answered

How is a car payment calculated?

The lender amortizes the loan: the amount financed (price minus down payment and trade-in, plus sales tax and fees) is spread over the term at a fixed monthly interest rate (APR ÷ 12). Early payments are mostly interest; later ones are mostly principal. The formula is payment = P·r·(1+r)ⁿ ÷ ((1+r)ⁿ − 1).

What APR can I get on a car loan?

It depends on your credit score, the loan term, and whether the car is new or used. Excellent credit can see rates well under the national average; subprime borrowers pay much more. Always get pre-approved by your own bank or credit union before visiting the dealer — it gives you a rate to beat.

How long should a car loan be?

Keep it at 60 months or less if you can. Loans of 72 or 84 months lower the monthly payment but cost thousands more in interest and leave you 'underwater' — owing more than the car is worth — for years, since cars depreciate faster than the loan shrinks.

Does a trade-in lower my payment?

Yes, two ways. The trade-in value reduces the amount you finance, and in most states it also reduces the taxable price, so you pay less sales tax. This calculator applies both. Confirm your state's tax rule — a few states tax the full price.

Does a manufacturer rebate lower my sales tax?

Usually no. A rebate (manufacturer cash incentive) reduces the amount you finance, like a down payment — but in most states sales tax is calculated on the vehicle's price before the rebate is applied, so it doesn't reduce your tax. That's the opposite of a trade-in, which in most states does lower the taxable price. A few states tax after the rebate, so check your state's rule.

Should I put more money down?

A larger down payment lowers the loan, the monthly payment, and total interest, and it keeps you from going underwater. Aim for at least 10–20% down on a new car, which drops in value about 20% in the first year alone.