Guide
Does the 20/4/10 rule still work?
It's still a useful check, but many buyers can't meet all three parts. Here's how to use it without treating it as a pass/fail test.
What the rule says
- 20 — put at least 20% down.
- 4 — finance for no more than 4 years (48 months).
- 10 — keep total monthly car costs (payment, insurance, fuel and other running costs) at or under 10% of gross monthly income.
It's a rule of thumb, not a lending standard. Lenders will often approve far more than it allows.
Why it feels hard to meet
The 10% part includes insurance and fuel, not just the loan payment. On a $60,000 salary, 10% is $500 a month for everything. If insurance and gas already take $250, only about $250 is left for a payment. The 4-year limit raises the payment further compared with a 60- or 72-month loan.
How to use it anyway
- Treat each part separately. Missing one test is a signal to look closer, not an automatic no.
- The 10% test matters most. It's the one tied to your monthly budget. A bigger down payment or cheaper car helps it most.
- A longer loan lowers the payment but costs more. Compare the extra interest before stretching the term.
Check a specific car with the 20/4/10 rule calculator, see what price range your salary supports with the affordability by salary calculator, or compare loan lengths with the 60 vs 72 month calculator.
Educational estimates only — not financial, tax or legal advice. Results depend on the inputs you provide and simplified assumptions. Confirm rates, taxes and fees with lenders, dealers and insurers before making decisions.