Car Affordability Check
When is a car too expensive?
A car is unaffordable when the monthly payment plus insurance, fuel and maintenance eats too large a slice of your income, or when a thin down payment and long term leave you owing more than the car is worth. This check is the forward companion to the reverse affordability calculator, which works back from a payment you name to the maximum price.
- Loan term is 5 years — the 20/4/10 rule caps it at 4 years.
The 20/4/10 rule: at least 20% down, a loan of no more than 4 years, and total car costs at or below 10% of gross monthly income. Rates used: new-car APR 6.39% / used 11.43% (Experian State of the Automotive Finance Market, Q1 2026). Planning aid only — not financial advice.
Frequently Asked Questions
How do I know if I can afford a specific car?
Enter the car price, your down payment, loan term and rate, and your household gross income. The tool adds the loan payment to your insurance, fuel and maintenance and shows it as a percentage of your gross monthly income, then flags the deal if it breaks the 20/4/10 rule (20% down, 4-year loan, total car costs at or below 10% of income).
What is the 20/4/10 rule for cars?
The 20/4/10 rule is a common planning checkpoint: put at least 20% down, finance for no more than 4 years, and keep total car costs (loan payment plus insurance, fuel and maintenance) at or below 10% of your gross monthly income. It keeps the payment manageable and limits how long you are upside-down on the loan.
Why does the loan rate matter so much?
In 2026 the average new-car loan APR is 6.39% and the average used-car loan APR is 11.43% (Experian Q1 2026) — roughly double. A higher rate raises the monthly payment and total interest, so a cheaper used car can end up costing more per month than a new one. The tool uses your rate, defaulting to the new-car average.
How is this different from the reverse affordability calculator?
The reverse calculator starts from a monthly payment you can afford and works back to the maximum price. This Car Affordability Check starts from a specific car price and tells you whether it fits your income and budget — the forward view you need when you have a car picked out.
Related tools
Updated August 2026 · Planning aid only; confirm all details with your lender and insurer.
Where the affordability check breaks — and how to fix it
A car is not affordable because a lender approves it. It is affordable when the total monthly cost of keeping it on the road fits inside a sensible share of your income — and when a thin down payment has not left you owing more than the car is worth. This is the difference the check is designed to surface.
What counts inside the monthly number
The verdict is not based on the loan payment alone. Four lines are added together: the payment on the financed amount, insurance, fuel and maintenance. That total is then expressed as a share of gross monthly household income. Buyers who test only the payment routinely pass their own check and fail this one, because insurance on a newer or sportier car and fuel on a thirsty one can add the equivalent of a second payment.
Why the 20/4/10 rule exists
- 20% down keeps the loan smaller than the car's depreciating value for longer, which is what protects you from negative equity if the car is written off or you need to sell early.
- 4 years maximum limits how long you can stay upside-down. A car depreciates quickly in the first years; a long loan keeps you in the hole longer than the car is worth.
- 10% of gross income is a ceiling on total car cost, not on the payment. It exists so that a car cannot crowd out saving, rent or debt repayment.
The four ways a deal fails
- Thin down payment — the payment fits, the equity position does not.
- Long terms of 72 or 84 months used to lower the payment rather than the price.
- Insurance priced after the purchase instead of before it.
- Budgeting zero for maintenance on a used car that will need tyres, brakes or a timing belt inside the loan term.
What to change first when the check fails
Work down the list in order of leverage: increase the down payment, shorten the term, then lower the price — because a shorter term raises the payment but cuts total interest sharply, while a lower price improves all three gates at once. Shopping insurance before you choose the car is the cheapest fix of all: a quote on the exact trim and VIN, obtained before signing, has saved more buyers than any negotiation at the desk.
Run the forward and reverse views together
This check answers "can I afford this specific car?". The reverse calculator answers the other question — "what is the most car I should be looking at?". Use the reverse view to set the shopping range, then use this check on the specific listing in front of you, and confirm the recurring costs with the total cost of ownership sheet.
Frequently asked questions
Should the 10% ceiling use gross or take-home income?
Use gross household income, which is the convention the rule is written against. If you prefer a stricter personal standard, apply the 10% test to take-home pay — just apply it consistently so month-to-month comparisons stay meaningful.
Does a trade-in count toward the 20% down payment?
Only the equity in it. If you owe more than the trade is worth, the negative equity rolls into the new loan, raises the amount financed, and makes the 20% gate harder rather than easier.
Is the check still useful if I plan to pay cash?
Yes, with the payment set to zero. The test then reduces to whether insurance, fuel and maintenance fit inside the 10% ceiling — and it is worth running on the cash comparison tool as well, because a large cash purchase has an opportunity cost.