What is an auto loan?
An auto loan is a secured installment loan used to purchase a vehicle. The vehicle serves as collateral, and the borrower repays the principal plus interest in fixed monthly installments over the loan term.
Lenders consider the vehicle price, down payment, trade-in value, credit history, and interest rate when determining the loan amount and terms. The monthly payment depends on how much is financed, the interest rate, and the repayment period.
- The price of the car is the total purchase price before any down payment or trade-in.
- Money you have represents your available cash for a down payment.
- Trade-in value is the credit a dealer offers for your current vehicle.
How does a car loan work?
When you take out an auto loan, the lender pays the dealer the purchase price minus your down payment and trade-in credit. You then repay the lender in monthly installments over an agreed period.
Interest accrues on the outstanding balance. Early in the term, a larger share of each payment goes toward interest. As the balance decreases, more of each payment goes toward principal. Making extra payments or a larger down payment can reduce total interest and shorten the loan term.
Factors that affect your auto loan
Loan amount: the portion of the car price you finance after down payment and trade-in.
Interest rate: determined by credit score, loan term, lender, and market conditions.
Loan term: longer terms mean lower monthly payments but more total interest.
Sales tax: added to the purchase price and may be included in the financed amount.
Car loan payment formula
Monthly payments are calculated using the standard amortization formula for installment loans.
M = P x r x (1+r)^n / ((1+r)^n - 1), where M is the monthly payment, P is the loan amount (car price minus down payment and trade-in, plus applicable tax), r is the monthly interest rate (annual rate divided by 12), and n is the total number of monthly payments.
The loan amount equals the price of the car minus money you have minus trade-in value, with sales tax added in most cases.
- Higher down payments and trade-in values reduce the loan amount.
- Lower interest rates and shorter terms produce lower total interest costs.
- Sales tax is calculated on the purchase price minus trade-in value in many jurisdictions.
Example auto loan calculation
Consider a $35,000 car with $5,000 cash available and a $3,000 trade-in. With a 7% sales tax applied to the price after trade-in, the tax is $2,240. The loan amount is $35,000 - $5,000 - $3,000 + $2,240 = $29,240.
At a 5% annual interest rate over 60 months, the monthly interest rate is 0.4167%. The monthly payment calculates to approximately $551.82. Total interest over the loan term is about $3,869.20, and the total cost including tax and interest is about $42,109.20.
- Input your specific price, down payment, and trade-in values.
- Adjust the interest rate to match your credit profile.
- Compare different loan terms to find the right balance of payment and total cost.
How to use the auto loan payment calculator
Enter the car price, your available cash, trade-in value, sales tax rate, interest rate, and loan term. The calculator instantly estimates your monthly payment, total loan amount, and total interest paid.
Adjust any input to see how it affects the payment. Try a larger down payment, a lower interest rate, or a shorter term to find the most affordable financing option.
Tips for getting the best auto loan
- Shop around for the lowest interest rate from banks, credit unions, and dealer financing.
- Make the largest down payment you can afford without depleting your emergency savings.
- Check your credit report before applying so you can correct errors and improve your score.
- Compare loan terms: a 48-month loan may have a higher payment but much less total interest than a 72-month loan.
Pros and cons of taking an auto loan
Auto loans make vehicle purchases accessible without paying the full price upfront, letting you spread the cost over several years. They can also help build credit history when payments are made on time.
However, vehicles depreciate quickly, which can leave you owing more than the car is worth (negative equity). Interest costs add to the total purchase price, and missed payments can damage credit and lead to repossession.
When an auto loan makes sense
- You need a reliable vehicle for work, family, or daily transportation.
- You can afford the monthly payments within your budget.
- You have stable income and good-to-excellent credit for a competitive rate.
When to consider alternatives
- Buying a less expensive used vehicle with cash.
- Delaying the purchase to save a larger down payment.
- Using public transit, car-sharing, or ride-hailing if your driving needs are limited.
Frequently asked questions
The loan term significantly affects your monthly payment and total interest. Longer terms (72-84 months) have lower payments but more total interest. Shorter terms (36-48 months) have higher payments but less total interest and faster equity building.
A down payment of at least 10-20% of the car price is recommended to avoid negative equity from the start.
Trade-in value is applied directly to the purchase price, reducing the amount you need to finance or pay out of pocket.