Auto Loan Calculator
A car payment is calculated on what you finance, not on what the car costs. Sales tax, documentation fees, title and registration are added before anything is subtracted, which is why the payment a dealer quotes is routinely higher than the one a simple price-minus-deposit calculation predicts.
The calculator below takes each of those separately, so the monthly figure it produces is the one that appears on the contract rather than an underestimate you have to revise upward at the desk.
Calculate your real car payment
Enter the price, then tax and fees separately. Those two are what move the payment away from the number in the advertisement.
What actually gets financed
The amount financed is the vehicle price, plus sales tax on the taxable portion, plus dealer and government fees, minus your cash down payment and any trade-in allowance.
In most states a trade-in reduces the taxable price as well as the amount owed, so it is worth more than the same sum in cash — the calculator treats it that way. A handful of states tax the full purchase price regardless, which is worth checking with your own department of revenue before assuming the benefit.
| Line | Effect on the loan |
|---|---|
| Vehicle price | The base — negotiate this, not the payment |
| Sales tax | Added; usually on price minus trade-in |
| Documentation fee | Added; capped by law in some states, uncapped in others |
| Title and registration | Added; set by the state, not the dealer |
| Cash down | Subtracted directly |
| Trade-in allowance | Subtracted, and usually reduces the taxable amount too |
| Negative equity rolled in | Added — this is how a loan starts underwater |
Why negotiating the monthly payment costs you money
A monthly payment has three inputs a seller can move: price, rate and term. A buyer who states a target payment has told the seller which two to adjust, and lengthening the term is the easiest of them.
Stretching a loan from 60 to 84 months drops the payment substantially and raises the total interest by considerably more, while keeping you in negative equity for years longer. The payment goes down and the deal gets worse, which is exactly why the question is asked in that form.
Negotiate the out-the-door price first and settle financing separately, ideally with a pre-approval from your own bank or credit union in hand. A dealer who can beat that rate will, and you will know it was beaten rather than being told it was.
Term length and being underwater
A car depreciates fastest in its first two years, and a long loan amortises slowest in exactly that period. The two together are what produce a loan balance larger than the vehicle is worth — negative equity, or being underwater.
It matters because it removes options. You cannot sell without covering the gap, an insurance total loss pays the value rather than the balance, and rolling the shortfall into the next car starts the whole pattern one step deeper.
The practical guards are a larger down payment, the shortest term the budget genuinely supports, and gap insurance where the deposit is small. None of them is exciting and all three are cheaper than the alternative.
A useful test: at the halfway point of the term, would the loan balance be below a realistic private-sale price? If not, the term is too long for that deposit.
Rate, credit and the finance office
The advertised promotional rate on a new vehicle is a manufacturer subsidy available to buyers in the top credit tier, and it frequently excludes any other incentive. Taking the low rate can mean giving up a rebate worth more, which is an arithmetic question the calculator answers directly: run the loan both ways and compare the totals.
For used vehicles no such subsidy exists and the rate is set by credit and term. The spread between tiers is large enough that a few months of repair before buying can be worth more than any negotiation on price.
Everything offered after the price is agreed — extended warranty, paint protection, gap coverage, tyre plans — is a separate product with its own margin. Each is negotiable, each can usually be bought elsewhere for less, and none has to be financed at the loan rate.
The costs that are not in the payment
A payment that fits the budget and a car that fits the budget are different tests, and the gap between them is usually two to four hundred dollars a month. Run the second one before signing.
- Insurance, which varies enormously by model and is worth quoting before you buy rather than after.
- Fuel or charging, over the miles you actually drive.
- Maintenance and tyres, higher on performance trims and on large wheels than the same model suggests.
- Registration renewal, which in several states scales with vehicle value.
- Parking, tolls and any local vehicle tax.
Paying it off early
Almost all US auto loans are simple-interest and carry no prepayment penalty, so extra payments reduce the balance immediately and every subsequent month accrues less interest. Check the contract for a precomputed-interest clause, which is rarer and does not work that way.
The largest saving comes from extra payments made early, when the balance and therefore the interest portion are largest. An extra hundred dollars a month in year one is worth substantially more than the same amount in year five.
Tell the lender to apply extra amounts to principal. Left unspecified, many will treat an overpayment as an advance on the next scheduled payment, which changes the due date and saves you nothing.
Frequently asked questions
Only if they were financed, which is normal — sales tax, documentation fee, title and registration are usually added to the loan rather than paid separately. That is why a payment quoted at the dealership exceeds one calculated from the sticker price alone.
It lowers the payment and raises the total cost, and it keeps you in negative equity for longer because the loan amortises slower than the car depreciates. Take the shortest term the budget genuinely supports.
In most states it reduces the taxable amount as well as the balance, which makes it worth more than the same figure in cash. A few states tax the full price regardless — check with your state department of revenue.
Whichever is larger, which is an arithmetic question rather than a judgement. Run the loan at the promotional rate on the full price, then at your own bank rate on the price minus the rebate, and compare the totals.