Car Affordability Calculator — The 20/4/10 Rule
The average new car payment just hit a record $770/month, with auto debt nationwide now over $1.68 trillion — more than total student loan debt. The classic 20/4/10 rule keeps you out of that trap: 20% down, a loan of 4 years or less, and total car costs at or under 10% of your monthly take-home pay. This calculator works backward from your income to show the maximum price you can actually afford.
The 10% cap covers loan payment, insurance, gas and maintenance combined — this calculator shows the loan-payment budget only, so leave room under your total for the rest.
Uses the 20/4/10 budgeting rule, a widely-cited guideline, not a lender requirement. Actual loan approval depends on your credit, debt-to-income ratio and the lender's own criteria.
How to use this tool
- Enter your monthly take-home pay (after tax, what actually lands in your account).
- Add any down payment you've already saved.
- Use the default 7% rate or your actual pre-approved rate, and keep the term at 4 years or less per the rule.
- Press Calculate to see the maximum car price your budget can handle — treat this as a ceiling, not a target.
Frequently asked questions
What is the 20/4/10 rule?
A classic car-buying budget rule: put down at least 20%, finance for 4 years or less, and keep total monthly car costs (loan payment, insurance, gas, maintenance) at or under 10% of your take-home pay. Following all three keeps a car from quietly wrecking your budget.
Why does the average car payment matter to me?
It doesn't directly — but a record $770/month national average, alongside loans stretching past 84 months for nearly a quarter of new-car buyers, shows how normalized car overspending has become. The 20/4/10 rule exists precisely to keep you out of that pattern.
Why only 4 years for the loan term?
Longer loans (72-84+ months) lower the monthly payment but dramatically increase total interest and keep you "underwater" (owing more than the car is worth) for years. A 4-year cap forces the price down to something your income can actually support, not just stretch out.
Does the 10% include insurance and gas?
In the classic rule, yes — the 10% is your *total* car cost, not just the loan payment. This calculator budgets the full 10% toward the loan payment for simplicity, so in practice, leave some room under your result for insurance, fuel and maintenance.