Auto Loan Calculator
Prices a car loan properly, including the trade-in complications that dealerships are good at obscuring.
Inputs
Loan
Loan Name: what to call the loan, such as Civic. It labels the result and the debt if you add it to your budget. Left blank, it's called Auto Loan.
Principal: the price of the car.
Rate: your quoted or expected APR.
Term: the length of the loan in months, up to 84.
What you bring
Down Payment: cash down.
Trade-In Value: what the dealer gives you for your current vehicle.
Left on Trade-In: what you still owe on it.
Taxes and fees
Sales tax: your sales tax rate, as a percentage.
Title, registration and fees: the one-off costs of the purchase.
Both are optional, and both are usually financed with the car, so they change the payment and not just the total.
The trade-in fields matter
What you still owe on your trade-in comes off its value, and only the difference reduces the loan. If you owe more than it's worth, that difference is negative equity, and it doesn't disappear when you trade in. It gets added to the new loan.
This is where a lot of people quietly go wrong. You trade in a car worth $12,000 with $15,000 still owing, and the $3,000 gap rolls into your new financing. You're now borrowing more than the new car costs, on a car that starts depreciating immediately.
Sales tax works the other way. Most states charge it on the price less the trade-in value, so trading in saves more than it looks.
What you get
Estimated monthly payment, with the month the car is paid off. Beneath it are Financed, Term, and Rate.
The breakdown spells the arithmetic out so you can check it: Principal, less Down payment, less Trade-in, net of what's owed, plus Sales tax and Fees where you entered them, giving the Amount financed. Then come Interest over the term and Total paid.
Term length is the trap
Dealers negotiate on monthly payment because it's the number buyers care about, and a longer term can always make the payment lower.
A longer term means:
- ›A lower monthly payment
- ›Substantially more total interest
- ›Longer underwater, owing more than the car is worth, for years
That last one is what sets up the negative-equity problem on your next car. It's a cycle, and it starts with agreeing to a 72- or 84-month term because the payment looked fine.
Run the calculator at several terms and compare Interest over the term rather than the monthly payment.
Rate matters more than you'd think
A few percentage points on a five-year loan is a lot of money. Get a rate quoted by your own bank or credit union before you go to the dealer. You'll then have a number to compare their financing against, rather than accepting whatever's offered.
Add To Budget
Add To Budget adds the loan to your Budget Builder as a debt, with its name, the amount financed as the balance, the rate, and the monthly payment. You'll see Auto loan added to budget. with a Go To Budget shortcut.
Then rebuild. This is the step that changes minds: a payment that fits comfortably in your monthly cash flow can still push your debt-free date out significantly, and the plan will show you by how much.
Do it before you're sitting in the finance office.
The rest of the cost
The loan payment isn't the cost of the car. Also budget for:
- ›Insurance, which often rises sharply on a newer vehicle
- ›Fuel
- ›Maintenance and tires
- ›Registration renewals
Add these to Expenses. A widely used guideline keeps total vehicle costs (payment, insurance, fuel, maintenance) under 15–20% of take-home pay. If you're in the US, the Paycheck Calculator will give you that figure.