Purpose of the affordability screen
The calculator reserves part of gross income for total monthly debt, subtracts existing required debt payments, and converts the remaining payment capacity into estimated loan principal. Cash down is then added to show a preliminary price ceiling before taxes and fees.
A lender may use different income, debt, credit, collateral, term, and underwriting rules. A calculated amount is not an approval, recommendation, or indication that the full ownership cost fits the household budget.
Formula and rate convention
Maximum auto payment equals gross monthly income × entered total-debt limit minus existing monthly debt. Principal is the present value of that level payment for the entered number of months using the entered annual interest-rate assumption divided by 12.
The rate field is labeled as an estimated annual interest rate because a disclosed APR can include certain finance charges and need not equal the note rate used to allocate monthly interest. Use a lender's payment disclosure to check the result.
Loaded example
With $6,000 gross monthly income, $900 of existing debt, a 36% total-debt limit, 7.2% annual interest, a 60-month term, and $5,000 cash down, payment capacity is $1,260 per month and the preliminary price ceiling is about $68,330 before taxes and fees.
Costs outside the ceiling
Sales tax, title and registration, dealer products, insurance, fuel, charging, maintenance, repairs, parking, and negative trade equity can materially reduce an affordable vehicle price. Keep these costs outside the loan calculation unless they are explicitly financed, then evaluate the resulting monthly household cash flow.
The calculator rejects cases where existing debt already consumes the selected debt-service amount, rather than presenting the down payment alone as an affordable price.
Primary guidance and next checks
The CFPB explains how to assess an affordable auto loan, debt-to-income ratios, and why borrowers should compare more than monthly payments.
Check the candidate amount with Auto Loan Payment and Total Car Ownership Cost using the same vehicle and date.