Car Affordability Calculator

Run the upgrade.

1. 01

   Set a total transportation cost ceiling

   Cap total monthly vehicle cost (payment plus insurance, fuel, maintenance, and registration) at a fixed share of take-home pay, commonly cited guidance is around 10-15%, and adjust down if other debts are high.

   Monthly ceiling = take-home pay x target percentage

2. 02

   Estimate non-payment costs first

   Get an actual insurance quote for the specific vehicle, and estimate monthly fuel and a maintenance reserve based on the vehicle's age and reliability record.

3. 03

   Back into the maximum loan payment

   Subtract insurance, fuel, maintenance reserve, and registration/12 from your total ceiling to find the maximum you can allocate to a loan payment.

   Max payment = monthly ceiling − insurance − fuel − maintenance reserve − (registration/12)

4. 04

   Convert the payment into a purchase price

   Using a realistic interest rate quote and loan term (avoid terms longer than 4-5 years), calculate the maximum loan amount that produces your max payment, then add your down payment for total purchase price.

5. 05

   Stress-test against a rate or income change

   Recalculate affordability assuming a higher interest rate or a temporary income drop to confirm the payment still fits with margin.

6. 06

   Set your walk-away price

   Write down the maximum out-the-door price (including tax, title, and fees) you'll pay, and treat it as a hard limit during negotiation.