Auto Loan Calculator

How to Use This Auto Loan Calculator

The sticker price is not what you finance. Add sales tax, fees, your trade-in and any rebate, and see the payment you would actually sign for.

Start with the price you've agreed, not the one on the window. Then add your down payment, your state and local sales tax rate, and the fees: title, registration and whatever the dealer calls its documentation charge. One total for all of them is fine.

Two switches matter more than they look. The first one puts the tax and fees into the loan, or leaves them out so you pay them on the day. The second one decides if your trade-in comes off the price the tax is charged on, which depends on your state and is explained further down. Got a trade-in? Open that section and put in both what it's worth and what you still owe on it.

The term buttons cover the five lengths dealers actually offer, and you can type anything else. Below the result you'll find the schedule month by month or year by year, and the whole thing as a PDF, an image, a CSV or an Excel workbook. If you would rather start from a monthly budget than a price, the second tab does that, and there is a section on it further down.

How Your Car Payment Is Worked Out

A car loan is an ordinary amortizing loan. Once you know what you are borrowing, the payment comes from the same formula as any other:

M = P × [ r(1 + r)ⁿ ] ÷ [ (1 + r)ⁿ − 1 ]

• M is the monthly payment
• P is the amount financed
• r is the annual rate divided by 12, as a decimal
• n is the term in months

The work is in P. What you finance is the price, plus sales tax and fees if you're borrowing them, less your down payment, less any rebate, less whatever your trade-in is worth once the balance on it is cleared:

P = price + tax + fees − down payment − rebate − (trade-in − owed on it)

Each payment splits two ways. Interest is what you still owe multiplied by the monthly rate, and the rest comes off the balance. As the CFPB puts it, more of your payment goes to interest at the start and more to principal later. There's one case the formula can't handle: a 0% loan, where it divides by zero. The answer there is the amount financed split evenly across the months, and the calculator does that separately.

Auto Loan Example: $30,000 Car at 6% for 60 Months

Here is what the calculator gives you for a $30,000 car with $5,000 down, 7% sales tax, $500 of fees, and the tax and fees rolled into the loan.

The gap between $30,000 and $37,015.09 is the whole point of the exercise. Tax and fees add $2,600 before you've driven anywhere, and interest piles another $4,415.09 on top. None of that appears on the window sticker.

Trade-In and Sales Tax: What Changes by State

Sales tax on a vehicle is charged on the selling price, at your combined state and local rate. What varies between states is what counts as the selling price.

In most states, a trade-in comes off first. Washington's dealer guidance says plainly that the selling price "excludes trade-in property of like kind", so the tax is charged on the difference. On a $30,000 car with an $8,000 trade-in at 7%, that is tax on $22,000 rather than $30,000: $1,540 instead of $2,100. The trade-in is worth $560 more than its sticker value, purely in tax.

A handful of states don't allow it. California is the clearest example, and its guidance for dealers says the trade-in allowance "cannot be excluded from the amount on which tax is based", with a worked example of a $20,000 car and a $4,000 trade-in taxed on the full $20,000. That's what the second toggle is for. It's on by default because most people are in a state that allows the credit, but check your own state before you lean on the number.

What this calculator assumes: tax is charged on the price less the trade-in, if you leave the toggle on, and always on the price before any rebate. Local rates, county add-ons, caps on the trade-in credit and the rules for private sales all vary, and none of them are modelled here.

Rebates, Fees and What Ends Up in the Loan

A cash rebate always reduces what you borrow. What it does to your tax bill is a different question, and states disagree. California counts a manufacturer rebate as part of the dealer's gross receipts, so the tax is worked out before the rebate comes off. This calculator does the same, because an estimate that lands slightly high is easier to live with than one that lands low.

Fees are the part people forget. Title and registration go to the state and are more or less fixed. The dealer's documentation fee is the dealer's own charge, capped in some states and not in others. Put the total in and it flows through the same way tax does.

Then decide if you want to borrow them. Financing $2,600 of tax and fees on the example above costs $415.86 in extra interest over five years, and paying them at signing turns a $5,000 cheque into $7,600. Neither one is wrong. Seeing both is the point.

How Much Car Can I Afford?

Work backwards from the payment, not forwards from the price. The second tab takes the monthly figure you can live with and runs everything in reverse: payment to loan, loan to price, with the tax and fees lifted out along the way.

A $500 monthly payment at 6% over 60 months, with $5,000 down and 7% sales tax, buys about $28,376 of car. That is the number to walk onto the lot holding. A dealer will happily hit any payment you name by stretching the term, so the payment on its own tells you nothing; the price that payment supports at a sensible term is the part that matters.

Two things this does not know about. Insurance costs more on a newer or faster car, and it is not part of the loan. And a lender will almost certainly approve more than the figure here, which is exactly why it helps to arrive with your own. For borrowing that has no sales tax attached, the loan calculator does the same thing without the car arithmetic.

How Long Should a Car Loan Be?

Same $27,600 at 6%, three different terms:

Going from 36 to 84 months more than halves the payment and more than doubles the interest. The CFPB makes the same point with its own example, and adds that some financial experts recommend keeping a car loan to five years or less, because longer loans are more likely to leave you owing more than the car is worth.

That last part is the real risk, and it compounds. Cars lose value fastest in the first couple of years, and a long loan pays the balance down slowest over exactly that stretch. It is the opposite of a house, where a 30 year mortgage is normal precisely because the thing behind it tends to hold its value. Get those two curves the wrong way round and your next trade-in turns up with a debt attached. If the only way the payment works is 84 months, the honest reading is usually that the car is too expensive, not that the term is too short.

A middle path, same as on any other loan: take the term that keeps you safe and put something extra against the principal when you can. On the 60 month example, $100 a month extra clears it in 50 months and saves $808.35.

Auto Loan FAQ

Sources

Where the sales tax and loan claims on this page come from. The math is ours, and we set out how we do it in the methodology.

• Publication 34, Motor Vehicle Dealers — California Department of Tax and Fee Administration
• Trade-ins — Washington State Department of Revenue
• How do I compare auto loan offers? — Consumer Financial Protection Bureau
• What is amortization and how could it affect my auto loan? — Consumer Financial Protection Bureau

Reviewed by Usman Ali · September 2026