How Are Car Payments Calculated?

Figuring car payments is easy if you have the right calculator — it’s not easy math otherwise

car payment calculatorCar payment calculation is not simple math. It requires a rather complex business math formula that is not easily done by hand and most people are not capable, or not willing, to take it on. It’s not as simple as dividing loan amount by the number of months in the loan. Finance charges (interest), which change every month, must be accounted for.

It’s much easier to use a hand-held business calculator, such as the HP 12c or HP 17b, or, even better, use an easy online auto loan calculator which does the math for you.

To use a car loan calculator, you must know the amount being financed, the number of months you want to finance, and the interest rate. You’ll also need to know the down payment amount, if any, and the value of your trade-in vehicle, if any. You also need to know the sales tax rate that applies to your home location, not where you buy your car.

How Car Payments Work

It’s a fact of life. Anytime you borrow money for a car, a house, or for credit card purchases, the lender wants you to pay an extra amount (interest) for your use of his money. The more money you use (borrow), and the longer your payoff term, the more you pay.

The way in which car loan payments are calculated sets a fixed monthly payment figure that includes two parts: 1) a part that repays some of the principal ( the amount you borrow), and 2) a part that pays interest (finance charges) on your outstanding balance.

Since your loan balance (principal) decreases with each monthly payment, the amount of interest in your payment also decreases and the amount going towards your loan balance increases.

This means that in the early months of your loan, you pay a lot of interest and less principal. As you move toward the end of your loan, you pay less interest and more principal. In other words, you pay off your loan faster at the end than at the beginning.

No two month’s payments are exactly the same in the amounts of the two parts, although the total payment is always the same (except for possibly the last payment which is usually less).

One possible problem with the way that car loans are structured is that the small amount of principal being paid in the beginning of the loan term may not pay the loan balance down as fast as the value of the vehicle depreciates.

This means you may be “upside down” — you owe more on your loan than your car is worth — during much of your loan term, which can be a problem if you decide to go through an auto refinance, sell or trade before your loan is paid off, or nearly paid off. It can also be a problem if your car is stolen or totaled in an accident. Insurance companies pay you what the car is worth, not the amount you still owe on your loan.

If you decide on a long-term loan (more than 48 months), or have a high interest rate, or make little or no down payment, or roll over negative equity from a previous car loan, you are almost assured of being upside down for most of your new loan term.

Some banks and loan companies allow you to make extra payments or pay more each month toward principle, which ends your loan sooner, lowers total finance costs, and reduces the chance of being upside down. Contact your bank or loan company to make arrangements.

The interest rate that you pay on your car loan depends on your most current credit score. If you don’t know your credit score, you should get it before you go shopping for a car or apply for a car loan.