Free car affordability calculator, built on the 20/4/10 rule: 20% down, 4 years maximum, and all vehicle costs under 10% of gross income. It works backwards from your income to a sticker price — the opposite of how a dealership does it.
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Car affordability calculator (20/4/10)
Works backwards from your income to a sticker price, instead of forwards from a monthly payment the dealer chose.
The 20/4/10 rule: 20% down, 4 years maximum, and all vehicle costs under 10% of gross income. Running costs are a real input — get an insurance quote before shopping, not after. Educational tool, not financial advice.
Why backwards
A dealership never asks what car you can afford. It asks what monthly payment you are comfortable with, then engineers a loan — of whatever length is required — that hits the number. Stretching the term lowers the payment and raises the total cost, which is how a car that does not fit is made to feel like one that does.
Starting from income and ending at a price removes that lever entirely.
Running costs are an input, not an afterthought
The 10% cap covers the payment plus insurance, fuel and upkeep. That is the clause people skip, and it is why the calculator asks for running costs before it will tell you a price. Get an actual insurance quote before shopping rather than after — on some cars it moves the affordable price by thousands.
If running costs alone consume the whole 10%, the calculator says so plainly. That is a real answer: it usually means a cheaper car bought outright, or lower running costs, rather than a longer loan.
The number will look low
For most incomes, the affordable car is more boring than the approved car — and the gap between those two is the entire point. Lenders approve on their formula; 20/4/10 protects the rest of your budget.
The full worked example, including what a 72-month loan really costs, is in How Much Car Can You Actually Afford? If you would rather skip the loan entirely, see saving for a car instead of financing one.
Educational tool, not personalized financial advice. Your loan terms, insurance and local market will differ.