Auto Loan Calculator
Use this auto loan calculator to estimate what a car purchase could cost each month after you factor in the vehicle price, down payment, trade-in value, any existing loan payoff on your trade-in, APR, loan term, sales tax, dealer fees, and any manufacturer rebate or incentive.
It is built for practical car-buying planning in the US. You can compare loan structures, test how negative equity on a trade-in raises the amount you borrow, and see how taxes, fees, and a rebate all shape the monthly payment and the total cost of the loan.
The calculator uses the full vehicle price as the purchase price, applies sales tax to a separate taxable amount (with a toggle to reflect your state's rules), and then applies the down payment, net trade-in equity, and any rebate as credits against the financed amount. Trade-in tax treatment varies by state.
Results are planning estimates only. Taxes and fees may be included if entered, but dealer structures, state tax rules, lender fees, and actual auto loan offers can vary.
How to use this calculator
- Enter the vehicle price (the agreed selling price before taxes and fees).
- Add your expected down payment.
- Enter the trade-in value (what the dealer offers for your current vehicle) and, if you still owe on it, the amount owed on the trade-in. The difference is the net trade-in equity; a negative result means negative equity.
- Enter the APR and loan term in months.
- Enter the estimated sales tax rate. Use the toggle to choose whether the trade-in value reduces the taxable amount — on is common in many US states, off applies tax to the full vehicle price.
- Add dealer fees and any manufacturer rebate or dealer incentive.
- Review the monthly payment, net trade-in equity, amount financed, and the term comparison table to see how different loan terms affect the payment and total interest.
This works well for comparing deals on different vehicles, testing how negative equity affects borrowing, or seeing what a rebate does to the monthly payment versus a lower APR.
How it works
This calculator first estimates the full vehicle deal by combining the car price, estimated sales tax, and fees, then subtracting your down payment and trade-in value to find the amount financed.
It is designed for practical auto loan planning, so the focus stays on monthly payment, amount financed, total interest, and how the structure of the deal changes the loan cost.
Monthly payment formula
Monthly payment = A × r × (1 + r)n / ((1 + r)n − 1)
Main inputs in the estimate
- A
- Amount financed after vehicle price, tax, and fees are reduced by down payment and trade-in value
- r
- Monthly rate derived from the APR
- n
- Total number of monthly payments in the loan term
What the estimate assumes
- Sales tax is estimated from a separate taxable amount based on vehicle price minus trade-in value, but state tax rules vary.
- Fees are added to the deal total before cash down and trade-in credits reduce the amount financed.
- The loan estimate assumes a fixed APR and equal monthly payments over the full term.
- Registration, title costs, optional dealer products, and lender-specific fees are not fully modeled here.
Assumptions and limitations
- Sales tax is estimated on the vehicle price minus trade-in value by default, which is common in many US states. Use the toggle to apply sales tax to the full vehicle price if your state does not allow a trade-in credit on the tax base.
- The trade-in payoff is subtracted from the trade-in value to determine net trade-in equity. Only the trade-in value — not the payoff — affects the sales tax base.
- A cash rebate or incentive is applied after sales tax is calculated, reducing the amount financed directly. Some states apply tax before the rebate; local rules vary.
- Dealer fees are added to the purchase cost before credits are applied.
- The estimate assumes a fixed APR and equal monthly payments over the full loan term.
- If the combined down payment, net trade-in equity, and rebate exceed the total purchase cost, the amount financed is shown as $0.00 and no amortization schedule is displayed.
- Registration fees, title costs, optional warranties, and lender-specific fees are not modeled here.
- This calculator is for planning only. It is not a dealer quote, loan approval, financing offer, or affordability recommendation.
Example scenario
Use this example to see how a realistic car deal structure affects the monthly payment and total financing cost.
- Vehicle price:
$32,000 - Down payment:
$5,000 - Trade-in value:
$3,000/ Amount owed on trade-in:$0 - APR:
6.9%/ Loan term:60 months - Sales tax:
7%(apply trade-in before tax: on) - Fees:
$1,200/ Cash rebate:$0
With those inputs, the taxable amount is $29,000 (vehicle price minus
trade-in value), the sales tax is $2,030, and the total purchase cost before
credits is $35,230. After subtracting the $5,000 down payment and the
$3,000 net trade-in equity, the estimated amount financed is $27,230.00.
The estimated monthly payment is $537.90. Over 60 months the estimated total paid is $32,274.17, which includes about $5,044.17 in interest.
How the amount financed is calculated
The amount financed is the loan principal — what you actually borrow after all the credits are applied.
| Step | Item | Amount |
|---|---|---|
| + | Vehicle price | $32,000 |
| + | Sales tax (7% × $29,000 taxable) | $2,030 |
| + | Fees | $1,200 |
| = | Total purchase cost | $35,230 |
| − | Down payment | $5,000 |
| − | Net trade-in equity | $3,000 |
| − | Rebate / incentive | $0 |
| = | Amount financed | $27,230 |
The monthly payment uses the standard fixed-rate loan formula applied to the amount financed, the monthly rate (APR ÷ 12), and the number of months.
Negative equity example
If you owe more on your trade-in than it is worth, the net trade-in equity becomes negative and is added to the amount financed rather than subtracted.
Using the same inputs above but with a trade-in valued at $8,000 and a
payoff of $12,000:
- Net trade-in equity:
$8,000 − $12,000 = −$4,000 - Taxable amount:
$32,000 − $8,000 = $24,000(payoff does not affect tax base) - Sales tax:
$24,000 × 7% = $1,680 - Total purchase cost:
$32,000 + $1,680 + $1,200 = $34,880 - Amount financed:
$34,880 − $5,000 − (−$4,000) = $33,880
The negative equity rolls the $4,000 shortfall into the new loan, raising the monthly payment compared to the default scenario.
Monthly payment vs total cost
A lower monthly payment from a longer term or a rebate can look appealing, but the total paid over the life of the loan is what determines the real cost. The term comparison table in the results shows both the monthly payment and total interest for 36, 48, 60, 72, and 84 months using the same amount financed and APR, so you can compare the tradeoff directly.
Frequently asked questions
How is an auto loan calculator different from a general loan calculator?
An auto loan calculator adds vehicle-specific inputs like down payment, trade-in value, trade-in payoff, sales tax, rebates, and dealer fees. A general loan calculator is better for broad borrowing estimates that do not depend on a car deal structure.
How does a larger down payment affect my monthly car payment?
A larger down payment reduces the amount financed, which lowers both the monthly payment and the total interest paid over the loan term, assuming the APR and term stay the same.
Should I include taxes and fees in the estimate?
Yes, if you want a realistic financing estimate. Sales tax and dealer fees add directly to the purchase cost and therefore to the amount you may need to borrow.
How does trade-in value affect the amount financed?
The calculator subtracts net trade-in equity — trade-in value minus any amount owed on that vehicle — from the total purchase cost. If the trade-in has positive equity, it reduces the amount financed. If it has negative equity, the shortfall is added to the amount financed instead.
What happens if I owe more on my trade-in than it is worth?
That is called negative equity. The calculator subtracts the trade-in value from the payoff to find the net equity. A negative result means the shortfall is rolled into the new loan, increasing the amount financed and the monthly payment. For example, a trade-in valued at $8,000 with a $12,000 payoff creates $4,000 in negative equity that adds to the amount financed.
Does a trade-in value reduce the sales tax?
In many US states, sales tax is calculated on the vehicle price minus the trade-in value rather than the full price. This calculator applies that treatment by default and includes a toggle to turn it off for states that tax the full price. The trade-in payoff amount does not affect the tax base — only the trade-in value does.
How are rebates or incentives handled in this estimate?
Cash rebates and dealer incentives are applied after sales tax is calculated, directly reducing the amount financed. Some states tax the vehicle price before applying the rebate, so for those states the result here is a close estimate. Local rules vary and this is a planning tool only.
Why is my amount financed higher than the vehicle price?
Several factors can raise the amount financed above the sticker price. Sales tax and dealer fees add to the purchase cost. Negative trade-in equity rolls an existing loan balance into the new one. If the combined credits — down payment, net trade-in equity, and rebate — are not large enough to offset those additions, the financed amount exceeds the vehicle price.
Do longer auto loan terms lower the monthly payment?
Usually yes, but a longer term typically increases the total interest paid and can leave you owing more than the car is worth for a longer period. The term comparison table on this page shows the monthly payment and total interest for common terms side by side.
Is this a car affordability calculator?
No. This page estimates the financing side of a specific car purchase. It does not evaluate your income, budget, or how much car you can safely afford. Use the Car Affordability Calculator link after the results for that type of estimate.
Is this a lease calculator?
No. Lease payments use a different structure with concepts like residual value and money factor. This tool is for fixed-term vehicle loan estimates only.
Is this a lender quote?
No. This is a planning estimate only. Actual APR, taxes, dealer fees, lender fees, and loan terms will differ from a real lender offer.
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