How to use this calculator
- Enter the car’s negotiated price, your down payment, your trade-in’s value and anything you still owe on it.
- Enter your state’s sales tax rate and the dealer’s title, registration and documentation fees. Choose whether you’ll roll them into the loan or pay them up front.
- Enter the loan’s APR and term. You’ll see your monthly payment, the amount financed, total interest and what the car costs you in total, plus a comparison of loan terms.
Nothing you enter is sent anywhere: the math runs in your browser.
How the loan amount is worked out
Sales tax = (Price − Trade-in value) × Tax rate, in states that give a trade-in credit
Trade-in equity = Trade-in value − Amount still owed
Amount financed = Price + Tax + Fees − Down payment − Trade-in equity
Monthly payment = Amount financed × r ÷ (1 − (1 + r)−n), where r = APR ÷ 12 and n = months
If you pay tax and fees up front, they’re left out of the amount financed and added to the cash you need at signing. Most states charge sales tax only on the price after the trade-in is subtracted, but some tax the full price. Untick that option if your state does.
The total cost of the car is everything you hand over: your down payment, your trade-in equity, any tax and fees paid up front, and every loan payment.
Worked example
These are the numbers the calculator loads with: a $35,000 car, $4,000 down, an $8,000 trade-in that’s fully paid off, 6.5% sales tax, $900 in fees, and a 60-month loan at 7.5% APR.
| Vehicle price | $35,000 |
| Sales tax: 6.5% of $27,000 (price after trade-in) | $1,755 |
| Title, registration and fees | $900 |
| Down payment | − $4,000 |
| Trade-in equity | − $8,000 |
| Amount financed | $25,655 |
That gives a monthly payment of $514.07 and $5,189 in interest over five years. With the down payment and trade-in, the car costs $42,844 in total.
| Term | Monthly payment | Total interest | Total cost of car |
|---|---|---|---|
| 36 months | $798.03 | $3,074 | $40,729 |
| 48 months | $620.31 | $4,120 | $41,775 |
| 60 months | $514.07 | $5,189 | $42,844 |
| 72 months | $443.58 | $6,283 | $43,938 |
| 84 months | $393.50 | $7,399 | $45,054 |
Stretching to 84 months cuts the payment by about $120 a month compared with 60 months, but adds $2,210 in interest, and that’s at the same rate. Lenders often charge more for longer terms.
Watch out for negative equity
If you owe more on your trade-in than it’s worth, the difference is usually added to your new loan. In the example above, owing $11,000 on the $8,000 trade-in would add $3,000 to the amount financed, raising it to $36,655 and the payment to $734.49. You’d be paying interest on a car you no longer own, and you’d start the new loan owing more than the new car is worth.
Ways to pay less for a car loan
- Get preapproved before you visit the dealer. A rate from your bank or credit union gives you something to compare against dealer financing.
- Negotiate the price, not the payment. A lower payment can hide a longer term or a higher price.
- Put more down. A bigger down payment lowers the amount financed and the interest you pay.
- Keep the term as short as you can afford. The comparison table shows how much each extra year costs.
Frequently asked questions
How is a car loan payment calculated?
First the amount financed is worked out: price plus tax and fees, minus your down payment and trade-in equity. Then the standard amortization formula turns that amount, the APR and the term into a fixed monthly payment.
Should I include sales tax and fees in the loan?
Rolling them in means less cash at signing, but you’ll pay interest on them for the whole loan. Paying them up front costs less overall if you have the cash.
Does a trade-in lower my sales tax?
In most states, yes: tax is charged on the price minus the trade-in value. A few states tax the full price. Check your state’s rules and set the option in the calculator.
Is a 72- or 84-month car loan a good idea?
It lowers the payment but raises the total interest, and you’re more likely to owe more than the car is worth for longer. If you need a long term to afford the payment, consider a less expensive car.
Is my information saved or shared?
No. The calculator runs entirely in your browser. If you use “Copy link to results”, your numbers are stored only in that link, so share it only with people you trust.
This calculator is for education and planning. Tax rules, fees and loan terms vary by state and lender, and it isn’t financial advice. Confirm the final numbers on your purchase and loan documents.