How Much Car Can I Afford?

By the Duvora Tools team · November 7, 2026 · 6 min read · How we write our guides

Cars are the second-biggest purchase most people make, and it's easy to overspend because dealers focus on the monthly payment rather than the total cost. A simple rule of thumb — 20/4/10 — keeps your car from taking over your budget.

The 20/4/10 rule

• 20% down payment (at least 10% for a used car).
• 4 years (48 months) maximum loan term.
• 10% of gross monthly income, maximum, for total car costs — payment, insurance and fuel together.

It's conservative on purpose. Following it means you're unlikely to owe more than the car is worth, and you'll have money left for savings and emergencies.

Worked example

Say you earn $72,000 a year — $6,000 a month before tax.

1. 10% of $6,000 = $600 a month for all car costs.
2. Subtract insurance (say $150) and fuel (say $150): $300 a month left for the loan payment.
3. At 7% APR over 48 months, $300 a month supports a loan of about $12,500.
4. Add a 20% down payment and the car budget is roughly $15,500–$16,000, before tax and fees.

Stretch the same $300 payment over 60 months and you could borrow about $15,150 — but you'd pay more interest and owe money for an extra year. Check any scenario with the auto loan calculator, which includes trade-in, sales tax and fees.

Monthly payment vs car price

Roughly, at 7% APR with 20% down, here's what different payments can buy:

The long-loan trap

72- and 84-month loans are now common because they make expensive cars look affordable. The problem: cars lose value fastest in the first few years. On a long loan you can be "upside down" — owing more than the car is worth — for years. If you need to sell or the car is written off, you'd have to pay the gap out of pocket.

Don't forget the real cost of owning a car

• Insurance — get quotes before you buy; some models cost far more to insure.
• Fuel or charging.
• Maintenance and tyres — budget more for older cars.
• Registration, taxes and parking.
• Depreciation — the biggest cost of a new car, though you don't see it monthly.

How your credit score changes the price

Your APR often matters more than the sticker price. Here's the same $25,000 loan over 60 months at three different rates:

Moving from 12% to 6% saves about $4,400 — enough for a year of insurance and fuel. If your score is fair or poor, spending a few months paying down card balances before you buy can pay off.

How the down payment changes things

Take a $35,000 car financed at 7% for 60 months (leaving out tax and fees to keep it simple):

• With $7,000 down you borrow $28,000: about $554 a month and $5,270 of interest.
• With $15,000 down you borrow $20,000: about $396 a month and $3,760 of interest.

The bigger down payment lowers the payment by $158 a month and saves around $1,500 in interest. It also means you're much less likely to owe more than the car is worth.

New, used or certified pre-owned?

A 2–3 year old certified car is often the best value: someone else has absorbed the biggest drop in value, and you still get warranty cover.

The true cost of a car over five years

Here's what the $35,000 car with $7,000 down and a $28,000 loan at 7% for 60 months really costs over five years, using typical monthly estimates:

That's before registration, parking and repairs. The monthly cost is $934, not the $554 payment the dealer quotes — and on the 20/4/10 rule it would need a gross income of about $112,000 a year. Running numbers like this before you shop is the easiest way to avoid regret.

What about electric cars?

Electric vehicles often cost more to buy but less to run. Charging at home is usually cheaper per mile than petrol or diesel, and maintenance tends to be lower because there are no oil changes and fewer moving parts. On the other hand, insurance can be higher, and used EV values have been volatile. Apply the same 20/4/10 test, but replace the fuel estimate with your expected charging cost and get insurance quotes before you commit. Check whether tax credits, rebates or lower registration fees apply where you live, as these change often.

Applying the rule outside the US

The 20/4/10 rule works anywhere — just use your local currency and costs. In the UK, many buyers use PCP (personal contract purchase) or hire purchase rather than a traditional loan. PCP gives lower monthly payments but ends with a large optional "balloon" payment to keep the car. In Canada and Australia, long terms of 84 months or more are common, which makes the "4" in 20/4/10 even more worth sticking to. Whatever the product, compare the total amount payable, not just the monthly figure.

Should you pay cash?

Paying cash means no interest and no risk of owing more than the car is worth. It makes sense if you can do it and still keep a full emergency fund. If paying cash would empty your savings, a modest loan and a healthy cushion is safer. And if a dealer offers 0%–2% promotional financing, borrowing while keeping your cash in a high-yield savings account can come out ahead — as long as the promotion doesn't come with a higher car price.

Get the most for your trade-in

• Know its value first using several online valuation tools, and get an instant cash offer from at least one car-buying service.
• Negotiate the new car's price and the trade-in separately so one isn't hidden in the other.
• Clean it and fix small issues; first impressions affect offers.
• Check your state's sales tax rule. Where tax is charged on the price minus the trade-in, trading in can save you tax compared with selling privately.

Common car-buying traps

• "What monthly payment are you looking for?" Dealers ask this so they can stretch the term to hit your number. Answer with the out-the-door price you want to pay instead.
• Rolling negative equity into the new loan. If you owe more on your trade-in than it's worth, that debt gets added to the new car loan — you start the new loan already behind.
• Payment packing. Extended warranties, gap insurance, paint protection and service plans are added to the loan, quietly raising the payment. Ask for an itemised price.
• Yo-yo financing. You drive away believing financing is approved, then get called back to sign at a higher rate. Get pre-approved so you have a firm offer.
• Buying on emotion. Set your price before the test drive and be willing to walk away.

A step-by-step car buying plan

1. Set your budget with the 20/4/10 rule and the true-cost table above.
2. Check your credit report and fix errors.
3. Get pre-approved by a bank or credit union.
4. Research models for reliability, insurance cost and resale value.
5. Get quotes from several dealers by email, on the out-the-door price.
6. Test drive, then negotiate price first, trade-in second, financing last.
7. Read the contract for add-ons before you sign.

Five ways to pay less

1. Get pre-approved by a bank or credit union before visiting the dealer.
2. Negotiate the price, not the payment.
3. Consider a 2–3 year old car: someone else has absorbed the steepest depreciation.
4. Improve your credit score first if you can — clearing card balances helps. See the credit card payoff calculator.
5. Skip the add-ons rolled into the loan unless you really want them.

Key takeaways

Frequently asked questions