About the 20/4/10 Affordable Vehicle Calculator
Use this tool to estimate a vehicle purchase price that stays within the 20/4/10 guideline: 20% down, a 4-year loan, and a payment no higher than 10% of gross monthly income. It is helpful for car shoppers comparing income, savings, and interest rate assumptions before setting a budget.
How to use this calculator
- Enter your gross yearly pay in dollars.
- Enter the savings available for the vehicle down payment.
- Enter the estimated APR for the auto loan.
- Click Calculate to see the affordable vehicle price and limiting factor.
- Click Reset to restore the default example values.
How it works
The calculator first converts gross yearly pay to gross monthly income, then sets the monthly payment limit at 10% of that amount. It uses the entered APR and a 48-month loan term to estimate the largest loan that payment can support.
It also checks the down-payment side of the rule by dividing available savings by 20%, since the savings are treated as the maximum down payment you can use. The affordable vehicle price is the lower of the price supported by the payment limit and the price supported by your savings.
The displayed down payment is 20% of the affordable price, and the estimated monthly payment is calculated on the remaining 80% financed over 48 months. The estimate excludes taxes, title, registration, insurance, maintenance, trade-ins, and lender fees, and it is educational only, not financial advice.
Example calculation
Suppose your gross yearly pay is $72,000, savings are $8,000, and the estimated APR is 7.0%. Gross monthly income is $6,000, so the 10% payment cap is $600 per month. At 7% APR over 48 months, that payment supports a loan of about $25,140, or a vehicle price of about $31,425 with 20% down. Your $8,000 savings can support up to a $40,000 price, so the income/payment cap is binding and the affordable vehicle price is about $31,425.
Frequently asked questions
What is the 20/4/10 car buying rule?
It is a budgeting guideline that suggests putting at least 20% down, financing for no more than 4 years, and keeping the car payment at or below 10% of gross monthly income.
Does this calculator include insurance or taxes?
No. It excludes taxes, title, registration, insurance, maintenance, trade-ins, and lender fees, so the actual total cost of ownership may be higher.
Why is my savings the limiting factor?
If your available savings are not enough to cover 20% down on the income-supported price, the calculator lowers the affordable price to the amount your down payment can support.
Why does APR change the affordable price?
A higher APR increases the monthly payment for the same loan amount, so the 10% income cap supports a smaller loan and potentially a lower vehicle price.
Should I use gross or take-home income?
The calculator follows the 20/4/10 rule using gross yearly pay. Using take-home income instead would create a more conservative estimate.