How to use the auto loan calculator
Enter the negotiated vehicle price, then subtract any down payment and trade-in credit. Add the sales tax rate that applies to the scenario, followed by the loan interest rate and term.
The calculator estimates the amount financed first, then applies the standard fixed-payment loan formula. Compare both the monthly payment and total interest. A longer term can reduce the payment while increasing the total borrowing cost.
Fixed-payment auto loan formula
This model adds sales tax to the vehicle price before subtracting the entered down payment and trade-in credit. Real transactions can tax trade-ins differently by state, so compare the modeled amount financed with the dealer worksheet before relying on the estimate.
APR can include costs beyond the note rate in some offers. This calculator uses the entered rate as the rate applied to the loan balance, so compare the result with the lender's disclosure before signing.
Example: Maya compares two car loan terms
Maya chooses a $30,000 car, pays $5,000 upfront, and has no trade-in. At a 5% sales tax rate, the tax is $1,500, so the amount financed is $26,500.
With a 6% annual interest rate, a 60-month loan costs about $512.32 per month. Extending the same balance to 72 months reduces the payment to about $439.18. The longer term costs more interest overall, even though the monthly payment is smaller.
Compare the term as well as the car payment
A longer term can lower the monthly payment while increasing total interest. Compare the same vehicle price, down payment and annual rate across two terms.
Use net trade-in credit after any outstanding loan. The tool estimates sales tax on the vehicle price; it does not determine local trade-in tax credits.
Assumptions and limitations
What the estimate assumes
Dealer fees, registration, warranties, add-ons, rebates, and state-specific tax treatment are not calculated automatically.
Important limitation 2
This is a fixed-rate planning model, not a lender quote or approval.
Sources and reference material
Auto Loan Calculator FAQs
What should I use for the auto loan interest rate?
Use the annual rate that will actually be applied to the financed balance. If an offer lists both an interest rate and APR, check the lender disclosure because APR can include certain finance charges in addition to interest.
Does a longer car loan lower the monthly payment?
Usually, yes. Spreading the same principal across more months lowers the required payment, but it generally increases the amount of time interest accrues.
Does the calculator include a trade-in?
Yes. The entered trade-in credit reduces the modeled amount financed after the sales-tax estimate. Actual tax treatment of trade-ins varies by jurisdiction.
Does this include dealer fees?
No. Add dealer fees and other financed charges to the vehicle price if you want them included in the modeled balance.
How much car can I afford based on a monthly payment?
A payment target can help narrow a vehicle budget, but affordability also depends on insurance, fuel, maintenance, registration, parking, and other household obligations. Work backward from a total transportation budget rather than treating the loan payment as the only cost.
For planning and educational use. Taxes, fees, lender disclosures, and financing terms can differ from this estimate.