How Much Car Can I Afford? (20/4/10 Rule)
A car payment is not the whole cost of a car. This calculator applies the 20/4/10 rule — 20% down, a loan of 4 years or less, and total monthly car costs under 10% of your gross income — to find the price you can actually afford.
Maximum Affordable Car Price
How It Works
The 20/4/10 rule is a widely used personal-finance guardrail for buying a car without letting the car own your budget. It has three parts: put at least 20% down, take a loan of no more than 4 years, and keep your total monthly car costs at or under 10% of your gross monthly income. The 10% is the part most buyers miss — it covers the loan payment plus insurance, fuel and maintenance, not the loan payment alone. The calculator works backwards from that 10% ceiling: subtract your monthly insurance and other running costs, and what is left is the loan payment you can afford. That payment, the loan term and the APR then fix the biggest loan you can carry, and dividing by the financed share (80% with a 20% down payment) gives the maximum car price.
The loan maths is the standard present-value formula: the most you can borrow is the monthly payment multiplied by (1 − (1 + r)−n) ÷ r, where r is the monthly interest rate and n is the number of monthly payments. A lower rate or a longer term raises the loan you can carry — which is exactly why the rule caps the term at 4 years: stretching to 6 or 7 years buys a dearer car but piles on interest and keeps you owing more than the car is worth for longer.
Worked Example
Take a gross annual income of $72,000, so gross monthly income is $6,000 and the 10% ceiling is $600 a month for everything car-related. With monthly insurance and other running costs of $150, the loan payment budget is $600 − $150 = $450 a month. Over 4 years (48 payments) at 7% APR, the monthly rate is 0.07 ÷ 12 = 0.5833%, and the present-value factor is (1 − 1.005833−48) ÷ 0.005833 = 41.76 — so the maximum loan is $450 × 41.76 = $18,792.09. With a 20% down payment, that loan covers 80% of the price, giving a maximum car price of $18,792.09 ÷ 0.80 = $23,490.11, with a down payment of $4,698.02. The total interest over the 4 years is 48 × $450 − $18,792.09 = $2,807.91.
Maximum Car Price by Income
The table below shows the maximum affordable car price at different gross incomes, holding the other assumptions fixed (20% down, 4-year loan, 7% APR, $150 a month of insurance and running costs):
| Gross annual income | 10% monthly budget | Loan payment budget | Max car price |
|---|---|---|---|
| $40,000 | $333 | $183 | $9,570.05 |
| $50,000 | $417 | $267 | $13,920.07 |
| $60,000 | $500 | $350 | $18,270.09 |
| $72,000 | $600 | $450 | $23,490.11 |
| $80,000 | $667 | $517 | $26,970.13 |
| $100,000 | $833 | $683 | $35,670.17 |
| $120,000 | $1,000 | $850 | $44,370.21 |
Every $10,000 of gross annual income adds roughly $4,350 to the car price you can afford under these assumptions — but note how much of the budget the $150 of running costs eats at lower incomes: at $40,000 a year it takes nearly half of the 10% ceiling, leaving only $183 a month for the loan itself.
Assumptions — and What This Calculator Leaves Out
- The 7% APR is an example rate, not a market average. Your actual rate depends on your credit score, the lender and whether the car is new or used. Replace it with your real quote — a higher rate shrinks the affordable price.
- Running costs are your estimate. The $150 default covers insurance and routine costs for a modest car; a newer or more powerful car, a young driver, or a long commute can push it much higher.
- Taxes, title, registration and dealer fees are not included. These typically add several percent on top of the sticker price, so treat the result as a price ceiling before those charges — or add them to your down payment budget.
- No trade-in or existing loan is counted. A trade-in effectively raises your down payment; an existing car loan counts against the 10% ceiling.
- Gross income is used, as the rule is written. The 10% is of pre-tax monthly income, so the ceiling is a planning figure — check it against your actual take-home budget — the Budget Planner maps your monthly budget on the 50/30/20 rule.
How to Use This Calculator
Enter your gross annual income, the down payment percentage you plan to make, the loan term in years, the APR your lender quotes, and your monthly insurance plus other running costs. The result shows your total monthly car budget, the loan payment you can afford, the maximum loan, the maximum car price and the down payment it needs. Change any input and the result updates live. Reset restores the worked example ($72,000 income, 20% down, 4 years, 7% APR, $150 running costs).
Tips and Practical Advice
Do not let a dealer stretch the term to make a dearer car "affordable": a 7-year loan on the same $450 payment supports a bigger loan, but you pay far more interest and spend years owing more than the car is worth. Get your insurance quote before you buy, not after — the difference between insuring a sensible hatchback and a sporty SUV can be $100 a month, which moves your affordable price by thousands. And if the calculator's answer is lower than the car you want, the honest fixes are a bigger down payment, a cheaper car, or waiting: a 20% down payment also protects you, because cars lose value fastest in the first year and a small down payment leaves you underwater almost immediately.
Frequently Asked Questions
What is the 20/4/10 rule?
It is a personal-finance rule of thumb for buying a car: put at least 20% down, take a loan of no more than 4 years, and keep total monthly car costs (loan, insurance, fuel, maintenance) at or under 10% of your gross monthly income.
Does the 10% include insurance?
Yes — the 10% covers everything the car costs each month, not just the loan payment. Insurance, fuel and maintenance all count, which is why the calculator subtracts your monthly running costs before working out the loan you can afford.
Is a 4-year loan always better than a 5-year loan?
For total cost, yes: a shorter term means less interest and less time owing more than the car is worth. A longer term lowers the monthly payment but raises the total interest and the risk of negative equity, which is why the rule caps the term at 4 years.
How much car can I afford on $60,000 a year?
At the table's assumptions (20% down, 4-year loan, 7% APR, $150 a month of running costs), a $60,000 income gives a $500 monthly budget, a $350 loan payment and a maximum car price of $18,270.09.
What if I already have a car loan?
Then the 10% ceiling is already partly used: subtract your current loan payment and running costs from the 10% budget before working out what a second car could cost — in practice, most people should pay the first loan off before taking another.
Sources: the 20/4/10 rule is a widely cited personal-finance rule of thumb; loan figures use the standard amortisation present-value formula. APR default (7%) is an example rate — replace with your lender's quote. Last reviewed: 13 November 2026.
Related guide: How Much Car Can I Afford? — the 20/4/10 rule and worked examples for every salary level.
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