Auto Loan Calculator

An auto loan lets you buy a vehicle now and repay it in fixed monthly installments over a set term. Each payment covers the interest due that month first, and the remainder reduces your principal balance. Early on, more of each payment goes toward interest; as the balance shrinks, more goes toward principal.

Three factors drive your monthly payment: the amount financed, the interest rate (often quoted as APR), and the length of the loan. Understanding how they interact helps you avoid paying more than you need to over the life of the loan.

Principal, rate, and term

The amount financed is the vehicle price minus your down payment and any trade-in value, plus anything you still owe on the trade-in. A higher price or interest rate raises your payment, while a longer term lowers the monthly payment. The catch is that a longer term also means you pay interest for more months, so the total cost climbs even though the monthly figure looks smaller.

The term-length trade-off

Stretching a loan to 72 or 84 months can make an expensive car feel affordable month to month, but you may pay thousands more in total interest. A shorter term carries higher monthly payments yet far less total interest and faster ownership. A good rule of thumb is to choose the shortest term whose payment comfortably fits your budget.

Negative equity: when you're underwater on a car loan

Negative equity — also called being underwater or upside down — means your loan balance is higher than the car is currently worth. To calculate it, subtract the car's market value from your remaining balance. For example, if you still owe $22,000 and the car is worth $18,000, you have $4,000 of negative equity.

When you trade in a car you are underwater on, the dealer pays off the old loan and the shortfall is added to the new one. Enter the trade-in's value and what you still owe on it above, and this works as a negative equity car loan calculator: it adds the gap to the amount financed and shows what it costs you. Here is the $4,000 from that example rolled into a $30,000 car financed over 60 months at 7.5% APR:

The old car keeps costing you on the new loan: about $80 a month and $809 in extra interest, and you start the new loan owing more than that car is worth too. Cars lose value fastest in their first few years, so long terms and small down payments make this far more likely. Paying the gap down before you trade, or waiting until the car is worth more than you owe, avoids the cost entirely.

Balloon payments on car loans

A balloon car loan keeps monthly payments low by deferring a large lump sum, the “balloon”, to the end of the term. Because your regular payments only pay down part of the balance, the rest comes due in one go with the last payment. Enter a balloon amount above to use this as a car balloon payment calculator: it shows the lower payment, the lump sum due at the end, and what the loan costs compared with a standard one.

The catch is interest. The balloon balance is never paid down, so you pay interest on it for the whole term. On a $30,000 loan over 60 months at 7.5% APR, a $10,000 balloon looks like this:

The payment drops by about $138 a month, and the loan costs about $1,727 more in interest. Before you sign, know how you will pay the balloon: savings, selling the car, or refinancing it. Refinancing depends on the car still being worth more than the balloon when it comes due, so for most buyers a standard amortizing loan, where every payment reduces the balance, is the safer and cheaper choice.

Down payment, trade-in, and total cost

A meaningful down payment or trade-in reduces the amount financed, lowering both your payment and total interest. Rates on new cars are often lower than on used ones, though used cars cost less overall. Remember the total cost of ownership too: insurance, fuel, registration, and maintenance all add up beyond the loan payment itself.

Monthly payment by loan amount

Here is what common amounts financed work out to at 7.5% APR, so you can sanity-check a payment before you ever sit down with a lender. These are principal and interest only — tax, title, registration and insurance sit on top.

Read across a row and the trade-off is obvious: a longer term always lowers the monthly figure, and always raises what the car costs you in total. We quantified that gap across every term in the Car Loan Cost Index.

What paying extra each month actually does

Overpaying is the simplest way to cut what a car loan costs, because every extra dollar goes straight at the principal — shrinking the balance that interest is charged on. On a $20,000 loan over 60 months at 7.5%, here is what different extra amounts achieve:

Two practical notes. Check your agreement for a prepayment penalty first — most US auto loans do not have one, but some do. And confirm the lender applies the extra to principal rather than holding it as next month’s payment, which achieves nothing.

When refinancing an auto loan makes sense

Refinancing replaces your current loan with a new one, ideally at a lower rate. It tends to be worth investigating when your credit score has improved since you bought, when market rates have fallen, or when you were financed at the dealership and never shopped the rate. Run your current balance and remaining term through the calculator above at a lower rate to see what the new payment and total interest would be.

Two cautions worth knowing. First, refinancing into a longer term can lower the payment while increasing total interest — the saving is only real if the rate drop outweighs the extra months. Second, if you have negative equity or a balloon payment coming due, refinancing is usually harder: lenders base the new loan on the car’s current value, so a balance above that value may not be fully refinanceable. In that case, paying the gap down first is generally the cleaner route.