Auto Loan Calculator
Calculate auto loan monthly payment, total interest, and total cost with trade-in and sales tax.
Written by Golam Rabbani, Founder & Lead Engineer
How to use this auto loan calculator
- Enter the vehicle price you negotiated with the dealer or seller.
- Add your cash down payment and any trade-in credit you expect to receive.
- Enter the loan term in months (commonly 36–84) and the APR your lender quoted.
- Add the local sales tax rate as a percentage so it is rolled into the loan amount.
- Press Calculate to see monthly payment, total interest paid, and total cost. Use Copy to save the result.
About this auto loan calculator
An auto loan calculator estimates your monthly car payment, total interest, and lifetime cost from the vehicle price, your down payment, trade-in value, the APR, and the loan term. It accounts for sales tax by adding the tax amount to the loan principal (the most common dealer-finance pattern in the U.S.), then amortizes the resulting balance over the term you select. The standard amortization formula is M = P × [r(1+r)^n] / [(1+r)^n − 1], where M is the monthly payment, P is the financed amount (vehicle price + sales tax − down payment − trade-in), r is the monthly interest rate (APR ÷ 12), and n is the loan term in months.
For example, a $32,000 vehicle with $4,000 down, a $3,000 trade-in, 6.5% sales tax, a 60-month term, and a 7.5% APR gives a loan amount of about $27,080, a monthly payment near $542.51, total interest around $5,470, and a total cost around $36,470. The U.S. Consumer Financial Protection Bureau publishes the same formula and warns about long terms increasing total interest — see consumerfinance.gov/consumer-tools/auto-loans/.
This calculator is for estimation only and is not financial advice — talk to a qualified financial advisor or your lender before signing a vehicle finance agreement.
FAQ
- How is sales tax handled?
- In most U.S. states, sales tax on a vehicle is rolled into the loan (you do not pay it separately at signing). This tool adds the sales-tax amount to the financed principal before amortizing. If your state taxes only the difference after trade-in, set sales tax to 0 and pre-compute it yourself.
- What APR should I use if I do not have an offer yet?
- Use the rate your bank or credit union pre-approved you for; if you do not have one, your credit score is the best proxy. Do not guess with online "average" rates — actual offers vary widely and using too-low a number will under-estimate the payment.
- Does a longer term lower my payment safely?
- It lowers the monthly payment but increases the total interest substantially, and you risk being "upside down" (owing more than the car is worth) for years. The CFPB recommends keeping auto loan terms as short as you can afford.
- How is trade-in different from down payment?
- Both reduce the amount you finance. Trade-in is non-cash credit from the dealer for your old vehicle; down payment is cash. The math treats them identically — they both shrink the loan principal.
- Is my data sent anywhere?
- No. The calculator runs fully in your browser. Numbers are not uploaded, stored, or logged.
- Should I rely on this for the final purchase decision?
- Use it for estimation only. Dealer add-ons (extended warranty, GAP insurance, doc fees) and lender-specific costs can change the financed amount. Always confirm the final numbers with the lender or dealer in writing.