Auto loan calculator

What is an auto loan calculator?

An auto loan calculator is a free online tool that estimates the fixed monthly payment on a car loan and shows how much you will pay in total over the life of the loan. By entering the price of the vehicle, your down payment, any trade-in value, the annual interest rate, and the length of the loan in months, you can see your monthly payment, the amount you actually borrow, the total of all payments, and the total interest before you sign anything.

Why the monthly payment matters

The monthly payment is the single number that tells you whether a car fits your budget, but it only tells part of the story. Two loans with similar monthly payments can carry very different total costs once the term and interest rate differ. Stretching a loan over more months lowers the monthly payment yet increases the total interest you pay. Seeing the payment, the total of payments, and the total interest side by side helps you balance affordability today against the true cost of the loan.

How does the auto loan calculator work?

You provide five pieces of information:

• The vehicle price (the agreed purchase price of the car).
• The down payment (the cash you pay up front).
• The trade-in value (optional; the credit for a vehicle you hand over).
• The annual interest rate, as a percentage.
• The loan term, in months.

The calculator subtracts the down payment and trade-in value from the price to find the loan principal — the amount you actually borrow. It converts the annual interest rate into a monthly rate, then applies the standard amortization formula to find a level monthly payment. From there it derives the total of all payments and the total interest paid.

Formula

The loan principal is:

$P = \text{price} - \text{down payment} - \text{trade-in}$

The monthly interest rate is the annual rate divided by 12:

$r = \frac{\text{annual rate}}{100 \times 12}$

With $n$ monthly payments, the level monthly payment $M$ is:

$M = \frac{P \cdot r \cdot (1 + r)^{n}}{(1 + r)^{n} - 1}$

When the interest rate is zero, the formula simplifies to:

$M = \frac{P}{n}$

The total of payments is $M \cdot n$, and the total interest is $M \cdot n - P$.

Worked examples

1. A car priced at $30,000 with a $5,000 down payment, no trade-in, a 6% annual rate, and a 60-month term:

   • Principal $P$ = 30000 − 5000 − 0 = 25000
   • Monthly rate $r$ = 0.06 / 12 = 0.005

   Calculation: $M = \frac{25000 \cdot 0.005 \cdot (1.005)^{60}}{(1.005)^{60} - 1} \approx 483.32$

   The total of payments is about $28,999.20 and the total interest is about $3,999.20.

2. A zero-interest loan with a principal of $12,000 over 24 months:

   • Principal $P$ = 12000
   • Annual rate = 0%, so $M = 12000 / 24 = 500$

   The total of payments equals the principal ($12,000) and the total interest is $0.

Notes

The calculator assumes a fixed interest rate and equal monthly payments, which is the most common structure for car loans. It does not include taxes, registration, dealer fees, or optional add-ons such as extended warranties or gap insurance, which can raise the amount you finance. A larger down payment or trade-in lowers the principal and therefore both the monthly payment and the total interest.

Compare related finance tools such as the APY calculator and the CAGR calculator to understand how interest rates compound over time.

FAQs

How does the loan term affect my payment?

A longer term spreads the principal over more months, which lowers each monthly payment but increases the total interest you pay over the life of the loan. A shorter term raises the monthly payment but reduces total interest.

Does a bigger down payment reduce interest?

Yes. The down payment (and any trade-in) reduces the principal you borrow, so you pay interest on a smaller amount. This lowers both the monthly payment and the total interest.

Is the interest rate here the same as APR?

The rate used in this calculator is the annual interest rate applied to the balance. A lender’s advertised APR may also fold in certain fees, so the APR can be slightly higher than the plain interest rate for the same loan.