A how much car can I afford calculator answers the question dealers ask backward: they start at payment; you should start at income. This tool works from gross monthly income and a payment cap (often 10–15% of take-home for the whole car, not just the note) or from a target monthly payment you already know you can carry.
Typical users are first-time buyers comparing a $400 truck payment to rent, parents sizing a teen’s first car, and anyone pre-approved at a credit union who wants a max vehicle price before stepping on the lot. A good outcome is a realistic ceiling on loan amount and sticker price after down payment, APR, and term — so “$450/month” does not quietly become a 84-month loan on a vehicle you cannot maintain.
This is a budget worksheet, not credit approval. Lenders use debt-to-income, credit score, and program limits. Use the number here as your walk-away line, then pair it with the all-in car budget calculator if insurance and fuel matter to your household.
Max payment = Income × (payment % ÷ 100)
Max loan = Payment × [(1+r)n − 1] ÷ [r(1+r)n]
Max price = Max loan ÷ (1 − down payment fraction)
Insurance, fuel, and repairs are not included — leave room in your real budget.
Payment-from-income uses the standard amortization inverse: given payment, rate, and months, principal = PMT × [(1+r)n − 1] ÷ [r(1+r)n]. Max price divides that loan by (1 − down payment fraction).
If APR is 0%, max loan = payment × months exactly. Edge case: payment too low for any positive-rate loan returns zero — raise payment or term.