How Much Car Can I Afford? The 20/4/10 Rule Explained

Financial experts recommend the 20/4/10 rule for car buying. Here's how to apply it — and how to calculate the exact car price that fits your income.

What is the 20/4/10 rule?

The 20/4/10 rule is a simple framework for car buying that financial planners have recommended for decades. It has three parts:

• 20% down payment — put at least a fifth of the car's price down to avoid being underwater on your loan.
• 4-year loan maximum — finance for no more than 48 months to limit total interest paid.
• 10% of income — keep total car expenses (payment + insurance) under 10% of your gross monthly income.

How to calculate your number

Let's walk through an example with a $70,000 annual salary:

Monthly gross income: $70,000 ÷ 12 = $5,833
Max car budget (10%): $5,833 × 10% = $583/month
Subtract insurance:   $583 − $150 = $433/month

At 6.5% APR over 48 months:
Max loan  ≈ $18,100
Plus 20% down (~$4,500 saved):
Max price ≈ $22,600

At $70K/year, the rule says you can comfortably afford a car in the $20,000–24,000 range. Many Americans buying $45,000 SUVs on this income are stretching dangerously.

Quick reference: income vs. car price

Annual Income	Max Payment	Max Car Price
$40,000	$333/mo	~$12,000
$55,000	$458/mo	~$18,000
$70,000	$583/mo	~$23,000
$90,000	$750/mo	~$31,000
$120,000	$1,000/mo	~$43,000

Assumes 6.5% APR, 48-month term, $150/mo insurance, $5,000 down.

When it's okay to bend the rules

The 20/4/10 rule is a guideline, not a law. You might reasonably deviate if you have no other debt, you're buying used (depreciation already absorbed), or you live somewhere with no transit alternative. That said, the 10% budget rule is the one to respect most — car expenses above 15–20% of take-home pay are the number-one reason people feel financially stretched.

Rule of thumb: if the monthly payment makes you hesitate, the car is too expensive — regardless of what the dealer approved you for.