Auto Loan Calculator
Work out your monthly car payment, including sales tax, fees and your trade-in.
Standard amortization formula ยท By Stuart Mathieson · Updated October 2026
Title, registration and dealer fees
Results
Monthly Payment
Amount Financed
Total Interest
Sales Tax
Total of Payments
Total Cost of the Car
The same loan over different terms
| Term | Monthly payment | Total interest |
|---|
Results are estimates for illustration only and are not financial advice. Consult a qualified financial professional before making financial decisions.
How the auto loan calculator works
First the calculator works out how much you need to borrow:
Sales tax is charged on the price - or, with the option ticked, on the price minus your trade-in, as many US states allow. The monthly payment then comes from the standard amortization formula, the same one the Loan Calculator uses. The total cost of the car is the price plus sales tax, fees and interest.
Worked example
A $35,000 car with $5,000 down, a trade-in worth $8,000 that still has $10,000 owing, 7% sales tax after the trade-in, $500 of fees, and a 6.9% loan over 60 months:
- Sales tax: ($35,000 − $8,000) × 7% = $1,890.
- Amount financed: $35,000 + $1,890 + $500 + $10,000 − $5,000 − $8,000 = $34,390.
- Monthly payment: $679.34, with $6,370.51 of interest over the 5 years.
- The trade-in has $2,000 of negative equity - more owed than it is worth - which is rolled into the new loan.
How the loan term changes the cost
The same $34,390 at 6.9%:
| Term | Monthly payment | Total interest |
|---|---|---|
| 36 months | $1,060.29 | $3,780.50 |
| 48 months | $821.92 | $5,062.00 |
| 60 months | $679.34 | $6,370.51 |
| 72 months | $584.67 | $7,705.91 |
| 84 months | $517.36 | $9,068.05 |
Stretching the loan from 60 to 84 months lowers the payment by $161.98 but adds $2,697.54 of interest - and because cars lose value quickly, a longer loan makes it more likely you will owe more than the car is worth.
Things to keep in mind
- Negative equity. Rolling what you still owe on your old car into the new loan makes the new loan bigger and more expensive. In CFPB data, borrowers who did this had average monthly payments about 26-27% higher than other buyers.
- Compare the whole deal. A lower payment can come from a longer term. Compare the total cost, APR and term - not just the monthly payment.
- Taxes and fees vary. Sales tax rates and how trade-ins are taxed differ between states and countries, so check the figures on your purchase agreement.
- Interest rate vs APR. Use the interest rate to find your payment; the APR includes some fees, so compare APRs between lenders.
Frequently asked questions
How long should a car loan be?
Shorter loans cost less overall but have higher payments. For $34,390 at 6.9%, a 48-month loan costs $5,062.00 in interest, compared with $9,068.05 over 84 months. Choose the shortest term whose payment fits your budget comfortably.
Does my trade-in reduce sales tax?
In many US states, yes - sales tax is charged on the price minus the trade-in value. Some states tax the full price, so untick the option if yours does.
What is negative equity?
Owing more on your current car loan than the car is worth. If you trade it in, the difference is usually added to the new loan, so you pay interest on it as well.
Sources
- Should I trade in my car if it's not paid off? - Consumer Financial Protection Bureau
- Data Spotlight: Negative Equity Findings from the Auto Finance Data Pilot - Consumer Financial Protection Bureau