💰 Car Affordability Calculator
Find out how much car you can afford based on income, debts, and 20/4/10 rule
How This Calculator Works
This calculator uses the 20/4/10 rule, the gold standard for affordable car buying: 20% down payment minimum to avoid being underwater immediately (cars lose 20% value in year 1). 4-year loan maximum to pay off the car before major repairs hit and avoid owing more than the car's worth. 10% of gross income maximum for total monthly auto costs (payment + insurance + gas + maintenance).
The calculator works backward from your income to determine the maximum car price you can afford. It calculates: 10% of monthly income = max total auto budget. Subtracts estimated insurance, gas, and maintenance. Remaining amount = max car payment. Using your down payment and loan terms, it determines the maximum purchase price that keeps you within the 20/4/10 guidelines.
Following this rule prevents common car-buying mistakes: being underwater on your loan, paying interest longer than the car lasts, and tying up too much income in a depreciating asset instead of building wealth.
Example Calculation
Real-World Example: $60,000 Annual Income
Income: $60,000 annual = $5,000 monthly gross income
10% Rule: Maximum $500/month for all auto costs
Estimated Costs: $140/month insurance (national average for good drivers), $150/month gas (15k miles/year at $3.50/gallon, 25 MPG), $80/month maintenance/repairs = $370 total fixed costs
Available for Payment: $500 - $370 = $130/month maximum car payment
Loan Calculation: 20% down, 7% APR, 48-month loan, $130/month payment supports ~$5,400 loan. Add 20% down ($1,350) = $6,750 maximum affordable car
Reality Check: This feels restrictive because most people violate the 20/4/10 rule. The average new car payment is $738/month - that requires $88,560 annual income under the 10% rule! Most buyers are financially overextended on vehicles. Stick to the rule and invest the difference in assets that appreciate, not depreciate.
Common Questions
Why only 4 years maximum loan term?
Cars depreciate rapidly: 20% in year 1, 15% year 2, 10% years 3-5. A 6-7 year loan keeps you "underwater" (owing more than car's value) for 3-5 years. If you total the car or need to sell, you owe money beyond the car's value. Plus, longer loans mean thousands more in interest. 4 years forces you to buy within your means and limits interest paid. If you can't afford the 4-year payment, you can't afford that car - buy cheaper.
Can I exceed 10% if I have no other debt?
You CAN, but you SHOULDN'T. Cars are depreciating assets - every dollar spent on a fancy car is a dollar not invested in assets that appreciate (stocks, real estate, business). Someone spending 15-20% of income on a car versus 10% loses hundreds of thousands in retirement wealth. Example: Invest the $300/month difference from age 25-65 at 7% returns = $720,000. That's the true cost of a nicer car. Buy cheaper cars, invest the difference, retire early and wealthy.
Should I buy new or used to maximize affordability?
Used wins financially. Buy a 3-5 year old car and let someone else absorb the brutal depreciation. A $35k new car loses $7k in year 1. Buy that same car 3 years old for $21k - it's lost most depreciation, still has good life left, and costs 40% less. Your insurance is cheaper too. With the 20/4/10 rule, buying used lets you afford more car OR bank the savings. Only buy new if you're wealthy enough that the premium doesn't impact your financial goals.