About this calculator

Auto Loan Payment is a free, single-purpose tool that answers one question well: what will this car actually cost me each month — and in total? It handles the parts most payment calculators skip: your trade-in, any loan still owed on it, and your state's sales-tax rules.

How the numbers are computed

The monthly payment uses the standard fixed-rate amortization formula — M = P × r(1+r)ⁿ / ((1+r)ⁿ − 1) — the same formula lenders and every major finance reference use, with monthly compounding. The amount financed follows the real dealer worksheet: vehicle price, plus sales tax and fees, minus your down payment and trade-in, plus any negative equity rolled over from the trade-in.

Sales tax uses 2026 state-level rates for all 50 states and DC, including each state's trade-in rule: most tax the price minus your trade-in, while a handful (California, Hawaii, Kentucky, Maryland, Michigan, Virginia, DC) tax the full price, Illinois caps the trade-in credit, and South Carolina caps the tax itself. Rates are compiled from state revenue and motor-vehicle agencies and reviewed annually. Local county and city taxes are not included — the rate field is editable so you can enter your combined rate.

Accuracy

The payment math is verified two ways: against a documented set of test cases, and independently by numerically solving the loan balance month by month and confirming both methods agree to a fraction of a cent. The amortization schedule always reconciles — principal rows sum exactly to the amount financed.

What this site is not

It is an estimator, not financial advice, a credit quote, or a loan offer. Your real APR depends on your credit; dealer fees and local taxes vary. Confirm final figures with your lender and your state's DMV or revenue department.