Auto Loan Calculator - Car Payment & Interest

The auto loan calculator estimates a car payment from vehicle price, sales tax, down payment, trade-in value, interest rate, and loan term. It separates the financed amount from the monthly payment so buyers can see how much principal is created before interest is added. The formula starts with Financed amount = vehicle price + sales tax - down payment - trade-in. The monthly payment then uses the standard installment loan formula Payment = P x r / (1 - (1 + r)^-n), where P is the financed amount, r is the monthly interest rate, and n is the number of monthly payments. Total interest is monthly payment times term minus financed amount, and total cost adds cash paid up front back to the loan repayment total. Use the car payment calculator before visiting a dealer, comparing lender quotes, or deciding whether a larger down payment or trade-in changes affordability enough to matter. It is also useful for seeing the cost of stretching a loan from 48 to 72 months: the payment may fall, but interest often rises and the borrower can stay underwater longer. The estimate does not include title fees, registration, dealer add-ons, insurance, maintenance, early payoff rules, or lender-specific rounding. Sales tax treatment varies by jurisdiction, especially when a trade-in is involved. Use the output as a clean financing comparison, then confirm taxes, fees, and final APR on the retail installment contract. A strong auto financing review compares the payment with the total interest and the total cost, not just monthly affordability. A lower payment from a longer term can look attractive while increasing interest and negative-equity risk. Buyers should also test a higher down payment, a lower vehicle price, and a better APR separately. Keeping each scenario documented makes it easier to negotiate with a dealer or lender without losing sight of the all-in cost. For best results, save the vehicle price, APR quote, term, down payment, trade-in allowance, and tax assumption with the result. Dealer worksheets can change quickly as warranties, fees, rebates, or add-ons are introduced. A documented calculation gives buyers a neutral reference point and helps separate the true financing cost from monthly-payment negotiation tactics.