Car Affordability: True Cost of Ownership
The sticker price is only part of what a car costs. Enter the price, loan terms, and running costs to see the true monthly cost and the 5-year total.
Last updated: October 2026
Car and loan details
The sticker price is only the start
Most car shoppers compare monthly payments. That is the wrong number. The number that decides whether a car fits your life is the true cost of ownership: the loan payment plus insurance, fuel, maintenance, and repairs, every single month. A $30,000 car with a $483 payment can easily cost $850 a month once the rest is counted, and that gap is where budgets break.
How the monthly payment is calculated
Auto loans use standard amortization: each payment covers that month's interest first, and the rest reduces the balance. The monthly payment formula is:
P is the amount financed (price minus down payment), r is the monthly interest rate, and n is the number of payments. A longer term lowers the payment but raises total interest, because you pay interest for more months on a balance that shrinks more slowly.
What goes into true cost of ownership
Beyond the payment, budget for four running costs. Insurance varies wildly by car, driver, and location: get a real quote before you buy, since a sporty coupe can cost double a sensible sedan to insure. Fuel depends on miles driven and MPG; EVs swap this for charging costs, which are usually lower but not zero. Maintenance covers tires, brakes, oil, and scheduled service. Repairs are the wildcard: budget more for older or high-mileage cars, and consider a pre-purchase inspection for anything used.
| Cost item | Monthly | 5-year total |
|---|---|---|
| Loan payment ($25,000 at 6% for 60 mo) | $483 | $28,999 |
| Insurance ($1,800/yr) | $150 | $9,000 |
| Fuel ($2,000/yr) | $167 | $10,000 |
| Maintenance ($800/yr) | $67 | $4,000 |
| Total with $5,000 down | $867 | $56,999 |
Worked example
A $30,000 car with $5,000 down at 6% APR for 60 months: the financed amount is $25,000, the monthly rate is 0.005, and the payment is 25,000 x 0.005 / (1 - 1.005-60) = $483.32. Total interest over the loan is $483.32 x 60 - $25,000 = $3,999. Add $150 insurance, $167 fuel, and $67 maintenance per month and the true monthly cost is $867. Over five years the car costs $5,000 down plus 60 months of $867, about $57,000 all in, nearly double the sticker price.
The 20/4/10 rule
Financial planners often cite the 20/4/10 rule: put at least 20% down, finance for no more than 4 years, and keep total car costs under 10% of gross income. The 20% down payment keeps you from going underwater (owing more than the car is worth). The 4-year cap limits interest and matches the loan to the car's reliable years. The 10% ceiling protects the rest of your budget. If the calculator's true monthly cost blows past 10% of your income, the car is too much car.
How to lower your true cost
Buy slightly used. A 2- to 3-year-old car has already taken its biggest depreciation hit, so you get most of the car for much less of the payment. Shorten the term. A 48-month loan at the same APR costs more per month but thousands less in interest. Shop insurance before you buy. Quotes for the exact car can change the monthly math by $100 or more. Raise the down payment. Every extra $1,000 down cuts about $19 a month off a 60-month loan at 6%, and it reduces interest too. Improve the rate. Check your credit, get pre-approved by a bank or credit union, and make the dealer beat it.
Car Affordability FAQs
What is a good down payment on a car?
Aim for at least 20% of the price on a new car and 10% on a used car. A bigger down payment lowers your monthly payment, reduces total interest, and keeps you from owing more than the car is worth as it depreciates.
How long should my auto loan term be?
48 months or less is ideal, 60 months is acceptable for a reliable car you plan to keep. Terms of 72 or 84 months lower the payment but pile on interest and keep you underwater for years. Never stretch the term just to afford a more expensive car.
What is the 20/4/10 rule for buying a car?
Put at least 20% down, finance for no more than 4 years, and keep all car costs under 10% of your gross income. It is a guardrail, not a law, but cars that break all three rules are the ones that wreck budgets.
Should I include depreciation in cost of ownership?
For monthly budgeting, no: depreciation does not come out of your paycheck. For the full financial picture, yes: a car that loses value fast costs you at resale or trade-in. This calculator focuses on cash costs, which is what affordability means month to month.
Is it cheaper to buy new or used?
Almost always used. New cars lose roughly 20% of their value in the first year. A 2- to 3-year-old car with a clean history gives you most of the useful life at a much lower payment, though you trade some warranty coverage and the newest features.
How does APR affect my car payment?
A lot. On a $25,000 60-month loan, 6% APR costs about $483 a month and $4,000 in total interest, while 10% APR costs about $531 a month and $6,870 in interest. That is nearly $2,900 extra for the same car, which is why rate shopping matters.
What credit score gets the best auto loan rates?
Generally 720 and above qualifies for the best rates from most lenders, with 670 to 719 getting decent but higher rates. Below 670, expect noticeably higher APRs. Check your score before shopping and get pre-approved so you know your real rate.