Question 1

When this is useful

Accepted Answer

Before you walk onto a forecourt or click "apply for finance". The dealer will tell you the biggest payment you qualify for; this tells you the price that actually fits your life. Set your price band first, then shop inside it.

Question 2

The 20/4/10 rule

Accepted Answer

A simple guardrail: put at least 20% down, finance for no more than 4 years, and keep total transport costs — loan payment, fuel, insurance, maintenance — under 10% of gross income. The 20% down keeps you from going underwater, the 4-year cap limits interest, and the 10% leaves room for the rest of your budget.

Question 3

Why running costs belong in the budget

Accepted Answer

A car payment is only part of the bill. Fuel, insurance, servicing, and registration can add hundreds a month. The calculator subtracts your running-cost estimate from the budget first, so the loan payment it leaves you is one you can genuinely sustain — not just one a lender will approve.

Question 4

A worked example

Accepted Answer

On $5,000 gross monthly income, 10% is a $500 transport budget. If running costs are $350 a month, only $150 is left for the loan payment — which at 8% over 4 years supports roughly $6,100 of loan. Add a $3,000 deposit and you are shopping around $9,000, not the $25,000 a lender might wave through. That gap is the entire point of the rule.

Question 5

Common mistakes

Accepted Answer

Stretching the loan to 6 or 7 years to afford a pricier car — you pay far more interest and stay underwater for years. Forgetting insurance and fuel in the budget. And treating the lender’s maximum as a target rather than a ceiling. Borrow for the car you need, not the most the bank will lend.

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