Short answer: the 20/4/10 rule says put 20% down, finance for no more than 4 years, and keep total car costs at or below 10% of your gross monthly income. On a $75,000 salary that means $625 a month for everything car-related. After about $375 a month for insurance, fuel and maintenance, about $250 is left for the payment — roughly a $10,440 loan at 7% over 48 months, or a $13,050 car with 20% down. The average new car costs $51,109 (Kelley Blue Book, October 2026) and needs roughly $162,000 a year of income to fit the rule.
Try it now: open the free Auto Loan Calculator and enter the car price, the down payment, the rate and the term. It works out the monthly payment, so you can test your own numbers against the 20/4/10 rule — no sign-up, no download.
The 20/4/10 Rule in Plain English
The rule has three parts, and all three have to hold at once. 20% is the down payment: pay at least a fifth of the price in cash before you borrow. 4 is the loan term in years: finance for 48 months or less, never stretch to 60 or 72 months to make the payment fit. 10% is the monthly cap: everything the car costs you — payment, insurance, fuel and maintenance — should stay at or below 10% of your gross monthly income, before tax.
It is a budgeting guideline, not a law and not a lender's cutoff. The average new-car buyer breaks it by a wide margin: the average monthly payment on a new car was $765 in the second quarter of 2026 (Experian), and the average new-car loan was $43,610. The rule exists because a car is a depreciating purchase.
What Counts in the 10%
The 10% covers the whole cost of owning the car, not just the loan payment: the loan payment, insurance (full coverage is usually required while a loan is outstanding), fuel and maintenance and repairs (tyres, brakes, servicing — small every month, large when they arrive).
The examples below use $375 a month for those three running costs combined — $150 for insurance, $150 for fuel and $75 for maintenance. That is an assumption for a modest car, not a quote — and if your running costs are higher, your affordable car price drops dollar for dollar.
What You Can Afford by Income — at 7% Over 48 Months
The table applies the rule at 7% — the average new-car APR in the third quarter of 2026 (Edmunds) — over 48 months, where each $1,000 borrowed costs $23.95 a month. Running costs are assumed at $375 a month, and the price assumes 20% down.
| Gross income | Monthly income | 10% total car cap | Left for the payment | Maximum loan | Maximum car price (20% down) |
|---|---|---|---|---|---|
| $60,000 | $5,000.00 | $500.00 | $125.00 | $5,220 | $6,525 |
| $75,000 | $6,250.00 | $625.00 | $250.00 | $10,440 | $13,050 |
| $100,000 | $8,333.33 | $833.33 | $458.33 | $19,140 | $23,925 |
| $125,000 | $10,416.67 | $1,041.67 | $666.67 | $27,840 | $34,800 |
| $150,000 | $12,500.00 | $1,250.00 | $875.00 | $36,540 | $45,675 |
On $60,000 a year the rule barely allows a car at all — a cheap used car bought mostly with cash.
Worked Example 1: $75,000 Income, Step by Step
Take a buyer earning $75,000 a year, buying with 20% down at 7% over 48 months. Monthly gross income is $75,000 ÷ 12 = $6,250.00; the 10% cap on total car costs is $625.00. Less $375 for insurance, fuel and maintenance, $250.00 is left for the loan payment. At $23.95 a month per $1,000 borrowed (7%, 48 months), the maximum loan is $250.00 ÷ $23.95 × $1,000 = $10,440, and the maximum car price at 20% down is $10,440 ÷ 0.80 = $13,050, with a $2,610 down payment.
The average new-car payment was $765 a month in the second quarter of 2026 (Experian) — more than the entire $625 monthly car allowance of a $75,000 earner, before insurance or fuel.
Worked Example 2: $100,000 — and the Average New Car
On $100,000 a year, monthly gross income is $8,333.33 and the 10% cap is $833.33. After $375 of running costs, $458.33 is left for the payment, supporting a loan of $19,140 and a car price of $23,925 with 20% down — a $4,785 down payment.
The average new vehicle cost $51,109 in October 2026 (Kelley Blue Book), up 2.1% from a year earlier. With 20% down, the loan is $40,887.20, and the payment at 7% over 48 months is $979.09. Add $375 of running costs and the total is $1,354.09 a month — which, at 10%, needs gross income of $162,491 a year.
Maximum car price at 20% down, by gross income — 7% APR, 48 months, $375 a month for insurance, fuel and maintenance.
How the Loan Term Changes the Answer
The 4 in 20/4/10 is the part buyers break most often, because a longer term is the easiest way to shrink the monthly payment. The table holds the loan at $25,000 and the rate at 7%:
| Loan term | Monthly payment | Total interest | Total paid |
|---|---|---|---|
| 48 months (the rule) | $598.66 | $3,735.49 | $28,735.49 |
| 60 months | $495.03 | $4,701.80 | $29,701.80 |
| 72 months | $426.23 | $5,688.21 | $30,688.21 |
Stretching from 48 to 72 months cuts the payment by $172.43 a month but adds $1,952.72 of interest — and the car depreciates fastest in the first three years, so a 72-month loan spends years underwater: you owe more than the car is worth. On $75,000 a year, the same $250 payment allowance supports a $14,664 loan over 72 months instead of $10,440 — a car price of $18,330 rather than $13,050 — but it costs $1,952.72 of extra interest.
How the Down Payment Changes the Answer
A bigger down payment shrinks the loan, the interest and the risk of going underwater. The table holds the car price at $30,000 and the rate at 7% over 48 months:
| Down payment | Cash down | Loan amount | Monthly payment | Total interest |
|---|---|---|---|---|
| 20% (the rule) | $6,000 | $24,000 | $574.71 | $3,586.07 |
| 10% | $3,000 | $27,000 | $646.55 | $4,034.33 |
| 0% | $0 | $30,000 | $718.39 | $4,482.59 |
Going from 20% down to nothing on the same $30,000 car costs $143.68 a month more and $896.52 more interest — and it starts the loan underwater from day one. With a fifth of the price already paid, the loan balance stays below the car's value for most of the term.
New vs Used
Used cars are cheaper to buy but more expensive to finance. In the second quarter of 2026 the average used-car APR was 11.19%, against 6.35% for a new car (Experian), and the average used-car payment was $542 a month against $765 for new. On a $25,000 loan over 48 months, the new-car rate of 7% gives a payment of $598.66 and $3,735.49 of interest; the used-car rate of 11.19% gives $648.45 a month and $6,125.47 of interest — about $2,390 more interest for the same amount borrowed.
That does not make new the better buy. A used car at $25,000 costs less than a new car at $51,109, so the loan is smaller even at the higher rate.
Five Mistakes That Break the Rule
1. Counting only the payment. The 10% covers insurance, fuel and maintenance too. 2. Using take-home pay. The rule is measured on gross income, before tax. 3. Stretching the term to fit the car. A 72- or 84-month loan makes any car "affordable" on paper while adding thousands in interest. 4. Putting little or nothing down. Zero down means the loan starts above the car's value. 5. Shopping by monthly payment alone. Dealers can hit any monthly payment by lengthening the term — always check the price, the rate and the term together.
When the Rule Bends
The rule is strict by design, and real life sometimes justifies bending it. A reliable car can be a genuine need — a long commute with no public transport, or a job that requires a vehicle. A buyer with no other debts, a large emergency fund and a stable income can carry a payment above 10% without real risk. And a 0% APR manufacturer offer changes the maths: with no interest, a longer term costs nothing extra.
What does not justify bending it is a nicer car. If the rule says $23,925 and the car you want is $35,000, the honest options are a cheaper car, a bigger down payment saved over time, or a higher income — not a longer loan. The rule bends for need and for safety margin, never for trim level.
Frequently Asked Questions
How much car can I afford on $75,000 a year?
About $13,050 with 20% down. The 20/4/10 rule allows $625 a month in total car costs; after about $375 for insurance, fuel and maintenance, about $250 is left for the payment, which supports a loan of about $10,440 at 7% over 48 months.
What is the 20/4/10 rule?
A car affordability guideline with three parts: put 20% down, finance for 4 years or less, and keep total car costs — payment, insurance, fuel and maintenance — at or below 10% of your gross monthly income.
How much car can I afford on $100,000 a year?
About $23,925 with 20% down: the 10% cap is $833.33 a month, and after $375 of running costs, $458.33 is left for the payment, supporting a loan of about $19,140 at 7% over 48 months.
What income do I need to afford the average new car?
About $162,491 a year. The average new car cost $51,109 in October 2026 (Kelley Blue Book); with 20% down, the $40,887.20 loan costs $979.09 a month at 7% over 48 months, plus $375 of running costs.
Is a 72-month car loan a bad idea?
Usually, yes. On a $25,000 loan at 7%, stretching from 48 to 72 months cuts the payment by $172.43 a month but adds $1,952.72 of interest, and the loan spends years underwater. A 0% APR offer is the main exception.
Does the 10% include insurance and fuel?
Yes — the 10% covers everything the car costs: the loan payment, insurance, fuel and maintenance. The examples here assume $375 a month for those three running costs combined.
Sources: Kelley Blue Book, average new-vehicle transaction price $51,109 in October 2026 (published November 10, 2026), up 1.3% from September and 2.1% year over year; Experian, State of the Automotive Finance Market, Q2 2026 — average new-car APR 6.35%, used-car APR 11.19%, average new-car payment $765 a month, average used-car payment $542, average new-car loan $43,610; Edmunds, Q3 2026 — average new-car APR 7.0%. All loan figures were verified by independent amortisation calculation at the stated rate and term; running costs of $375 a month are an assumption, not a quote. This article explains the maths and is not financial advice — confirm your rate with a licensed lender before you buy.
Related reading: How to Calculate an Auto Loan Payment · Lease vs Buy a Car: Which Costs Less? · Can You Deduct Car Loan Interest?
Working out what car you can afford? If you are weighing a car purchase or want help with the numbers before you apply for a loan, book a free consultation with Asad Webs — we will help you work out the figures before you sign.
Be the first to share a useful question or thought.