Auto Loan Calculator
Estimate your monthly car payment and total interest.
- Author
- CentCompass
- Last Updated
- Reading Time
- 4 min read
Loan amount
$30,000.00
Monthly payment
$594.04
Total interest
$5,642.16
Total of payments
$35,642.16
What is the Auto Loan Calculator?
An auto loan calculator estimates your monthly car payment and the total interest you will pay, based on the vehicle price, down payment, trade-in value, interest rate, and loan term. It separates the price of the car from the cost of borrowing to buy it — two numbers that dealers often blend together into a single monthly figure.
How the calculation works
The amount you actually finance is the vehicle price minus your down payment and any trade-in value. That figure is amortized over the loan term at your APR, producing a fixed monthly payment. Each month interest is charged on the outstanding balance and the rest of the payment reduces principal, exactly as with a mortgage. Because cars depreciate quickly while loans amortize slowly, a long term can leave you owing more than the vehicle is worth for much of the loan.
The formula
The financed amount is P = price − down payment − trade-in value. The monthly payment then follows M = P · [r(1+r)^n] / [(1+r)^n − 1], where r is the APR divided by 12 and n is the term in months. Total interest is M × n − P, which is the clearest single measure of what the financing itself costs you, independent of the car's price.
Worked example
A $35,000 vehicle with $5,000 down and no trade-in means financing $30,000. At 7% over 60 months the payment is about $594, and total interest comes to roughly $5,600. Stretching the same loan to 72 months drops the payment by around $80 but pushes total interest above $6,700 — you pay noticeably more to borrow the identical amount. That trade-off is the single most important comparison to make before signing.
Tips
- A larger down payment or trade-in cuts both the payment and the total interest.
- Negotiate the vehicle price and the financing separately so neither hides the other.
- Get a rate quote from your own bank or credit union before visiting the dealer.
- Compare APR rather than the monthly payment across offers.
- Keep the term as short as the payment allows — the interest saving is substantial.
Common mistakes
- Negotiating on the monthly payment, which lets a longer term disguise a worse deal.
- Forgetting sales tax, title, registration, and dealer fees, which are not in this estimate.
- Rolling negative equity from an old loan into the new one and starting underwater.
- Accepting dealer financing without checking an outside quote first.
- Overlooking insurance, which can differ by hundreds a year between similar vehicles.
Limitations
This estimate covers the loan only. It excludes sales tax, title, registration, documentation and dealer fees, extended warranties, and gap insurance, all of which vary by state and dealer and are often financed alongside the car. It also assumes a fixed rate, a trade-in with no outstanding loan against it, and no manufacturer rebate applied to the price.
Frequently asked questions
How is auto loan interest calculated?
Interest accrues on the remaining balance each month. Your fixed payment covers that interest first and the remainder reduces principal, so the interest portion shrinks over the life of the loan as the balance falls.
Does a trade-in reduce my loan?
Yes. The trade-in value is treated much like a down payment and subtracted from the price, reducing the amount financed. If you still owe money on the trade-in, only the equity above that balance helps you.
Is a longer term cheaper?
It lowers the monthly payment but raises the total cost, because you are borrowing the same money for longer. Longer terms also keep you underwater on a depreciating asset for more of the loan.
What APR should I expect?
It depends on your credit profile, the lender, the term, and whether the car is new or used. Used-car loans typically carry higher rates than new, and rates rise sharply as credit scores fall — which is why comparing several offers matters.
Are taxes and fees included?
No. Sales tax, title, registration, and dealer documentation fees vary by state and are not part of this estimate. Many buyers finance them, which increases the loan amount and the payment beyond what is shown here.
Should I take a cash rebate or low-APR financing?
Compare them numerically rather than by instinct. A rebate reduces the amount financed immediately, while promotional financing reduces the interest rate. Run the total cost both ways — the better option depends on the loan size and the gap between the rates.
What does it mean to be upside down on a car loan?
It means you owe more than the vehicle is worth, which happens when depreciation outpaces the loan balance. A small down payment and a long term make it far more likely, and it becomes a problem if you need to sell or the car is written off.
Can I pay off an auto loan early?
Usually yes, and because interest is charged on the outstanding balance, paying ahead reduces total interest. Check your contract for a prepayment penalty, which is uncommon on mainstream auto loans but not unheard of.
New or used — which is cheaper to finance?
New cars typically attract lower interest rates and sometimes subsidised manufacturer financing, but they depreciate much faster. A used car with a slightly higher rate often still costs less overall once depreciation is counted.
How does my credit score affect the payment?
Credit score is the main driver of your APR, and APR drives the payment. The difference between excellent and subprime credit on the same car can amount to thousands of dollars in extra interest over a five-year loan.
Related calculators
- Personal Loan Calculator
- Amortization Calculator
- Credit Card Payoff Calculator
- House Affordability Calculator
Related guides
Sources
- CFPB — Auto loans
- FTC — Financing or Leasing a Car
- Federal Reserve — G.19 Consumer Credit
How this page is produced
Editorial process. CentCompass is maintained independently, and this page is written and checked against the official publications listed above before it goes live. There is no separate editorial reviewer. This page was last checked on . See our editorial policy.
How the calculations work. Every result comes from a small, unit-tested calculation engine rather than a spreadsheet or a hardcoded table. Loans use the standard amortization formula, growth uses compound-interest math, income tax applies the federal progressive brackets, and payroll applies Social Security and Medicare rules. Our methodology sets out each one.
Where the figures come from. Tax brackets, standard deductions, FICA parameters, and contribution limits are stored once in a dated registry and read directly by the calculators — the same values appear in the text above, so the two can never drift apart. Each figure records its source, effective tax year, and review status on our data sources page.
Update policy. Regulatory figures are checked against their primary source when the IRS, SSA, or another authority publishes new values — typically each autumn for the following tax year — and again at the scheduled review date recorded for each dataset. Figures that have not been checked yet are marked as draft on the data sources page until that check is complete.
Educational purposes only — not financial, tax, or investment advice (disclaimer).