Car Affordability Calculator
Find the most you should spend on a car using the 20/4/10 rule.
The 20/4/10 rule
A popular guide says to put at least 20% down, finance for no more than 4 years, and keep total car costs under 10% of gross income. Total costs include the loan payment, insurance, fuel and maintenance. We solve for the price that fits that 10%.
Beyond the rule
A cheaper used car often saves the most money. Compare total ownership cost, not only the monthly payment.
Worked example
Last reviewed November 2026. Formulas are standard and shown in the sections above; results are estimates.
Tips and common mistakes
- Choose a used car to avoid the steepest depreciation.
- Shop for the loan before the car.
- Include insurance quotes before you buy.
Learn more
Frequently asked questions
Is 10% too strict?
It is a conservative guide. Some people go higher, but car costs squeeze other goals.
Does it include sales tax?
No. Subtract tax and fees from your price target.
What about leasing?
Compare the total cost with buying over the same period.
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