Auto Loan Calculator: How to Calculate Monthly Payments and Total Interest for Your Car Loan

Buying a car is one of the biggest financial decisions most people make. Whether you are financing a new sedan or a used SUV, understanding your auto loan before signing the paperwork can save you thousands of dollars in interest. The monthly payment is just one piece of the puzzle — the loan term, interest rate, and down payment all dramatically affect what you ultimately pay.

Get instant calculations with our Auto Loan Calculator — it shows your monthly payment, total interest, and full amortization schedule.

How Auto Loan Payments Are Calculated

Auto loans use a simple interest formula. Your monthly payment depends on three factors:

• Loan amount — The car price minus your down payment and trade-in value
• Interest rate (APR) — Your annual percentage rate based on credit score and lender
• Loan term — The number of months you have to repay (typically 36, 48, 60, or 72 months)

The formula used by lenders is:

Monthly Payment = P × [r(1+r)^n] / [(1+r)^n – 1]

Where P = principal loan amount, r = monthly interest rate (APR ÷ 12), and n = total number of payments.

Real-World Example: $30,000 Car Loan

Term	Rate	Monthly Payment	Total Interest	Total Cost
36 months	5.0%	$899	$2,369	$32,369
48 months	5.5%	$698	$3,518	$33,518
60 months	6.0%	$580	$4,799	$34,799
72 months	6.5%	$502	$6,164	$36,164

Notice that extending the term from 36 to 72 months lowers the monthly payment by $397 but adds $3,795 in extra interest. Always calculate the total cost, not just the monthly payment.

How Down Payment Affects Your Loan

A larger down payment reduces both your monthly payment and total interest. On a $30,000 car with a 60-month loan at 6% APR:

Down Payment	Loan Amount	Monthly Payment	Total Interest
$0	$30,000	$580	$4,799
$3,000	$27,000	$522	$4,319
$6,000	$24,000	$464	$3,839
$10,000	$20,000	$387	$3,199

Aim for at least 20% down payment to avoid being upside down on your loan from day one.

Tips for Getting the Best Auto Loan Rate

• Check your credit score before applying — scores above 720 qualify for the best rates
• Shop around — Get pre-approved from credit unions, banks, and online lenders before visiting the dealership
• Choose a shorter term if you can afford the payment — you will pay significantly less interest
• Negotiate the car price first, then discuss financing — never reveal your budget before the price is set
• Watch for add-ons — Extended warranties, gap insurance, and dealer fees add to your loan amount

Use the Auto Loan Calculator to compare different scenarios before you visit the dealership. Knowing your numbers puts you in control of the negotiation.