Car Affordability Calculator
How much car can you actually afford without straining your budget? This calculator applies the popular 20/4/10 rule — 20% down, a loan no longer than 4 years, and total auto costs under 10% of your gross income — to estimate a sensible price.
How this calculator works
The 20/4/10 rule has three parts:
- 20% down — enough to avoid being underwater as the car depreciates.
- 4-year loan max— longer terms cost more interest and keep you in debt past the car’s best years.
- 10% of income — your total monthly auto spending (loan payment plus insurance and fuel) should stay under 10% of gross monthly income.
We take 10% of your monthly income, subtract your estimated insurance and fuel costs to find the maximum loan payment, then reverse-amortize that over a 48-month term to get the largest loan. Adding your down payment yields the affordable car price.
Why total cost, not just the payment
Dealers quote monthly payments, but insurance, fuel, and maintenance are real and ongoing. The 10% cap covers all of it, which is why a higher insurance or fuel estimate lowers the price you can afford.
Learn more
- Leasing vs Buying a Car: Which Actually Costs Less? — Lower monthly payments vs building ownership — how leasing and buying really compare, the hidden costs of each, and who each option suits.
- Car Insurance Explained: What Coverage Do You Actually Need? — Liability, collision, comprehensive, uninsured-motorist — what each car-insurance coverage does, why state minimums are rarely enough, and how to choose limits and deductibles.
Frequently asked questions
- What is the 20/4/10 rule?
- A simple guideline for buying a car responsibly: put at least 20% down, finance for no more than 4 years, and keep total monthly vehicle costs (payment, insurance, fuel) under 10% of your gross income.
- Why only a 4-year loan?
- Longer auto loans lower the monthly payment but cost far more interest and often leave you owing more than the car is worth. Capping at 4 years keeps you building equity and avoids long-term debt on a depreciating asset.
- Is this the same as what a dealer will approve?
- No — dealers and lenders may approve much more. The 20/4/10 rule is a budgeting guideline for a payment you can comfortably sustain, not the maximum someone is willing to lend you.