Auto Loan Calculator: Estimate Your Car Payment
The auto loan calculator determines your monthly car payment, total interest cost, and full payoff schedule based on vehicle price, trade-in value, down payment, loan rate, and term. Car buyers at dealerships, consumers refinancing an existing auto loan, and parents helping young drivers make their first vehicle purchase use this tool to avoid overpaying. Key outputs include monthly payment, out-the-door loan amount, total interest paid, and a complete amortization schedule. Because dealers frequently negotiate on monthly payment rather than total price — obscuring the true cost of financing — this calculator lets you verify numbers independently and spot when a low payment conceals a high overall cost through term extension or hidden fees.
This calculator is for educational and informational purposes only. Results are estimates based on the inputs provided and do not constitute financial, tax, legal, or investment advice. Consult a qualified financial professional before making any financial decisions.
How This Calculator Works
The calculator starts with the vehicle sale price, subtracts your down payment and trade-in equity, then adds sales tax, dealer fees, and any aftermarket add-ons financed into the loan to produce the net loan amount. The standard amortization formula then computes the level monthly payment that retires that balance at the stated rate over the chosen term. The full schedule shows how each payment divides between interest and principal, and how quickly you build equity relative to the vehicle's expected depreciation — revealing exactly when (or whether) you cross into positive equity.
How to Use This Calculator
Enter the negotiated vehicle price (not sticker price—always negotiate first).
Enter your down payment amount.
Enter the APR from your bank, credit union, or dealer.
Select the loan term.
In Advanced Inputs, add trade-in value, sales tax rate, and dealer fees.
Review the total amount financed and monthly payment.
Check the balance vs. value chart to ensure you will not be underwater long-term.
Formula
Net Loan = Sale Price − Down Payment − Trade-In Value + Sales Tax + Fees. Monthly Payment M = Net Loan × r(1+r)^n ÷ [(1+r)^n − 1], where r = annual rate ÷ 12 and n = months. Equity at any point = Current Market Value − Remaining Loan Balance. Negative equity occurs when Remaining Balance exceeds Current Market Value.
Total Amount Financed
Loan = Price + Tax + Fees + TradeInOwed − TradeInValue − DownPayment − RebateWhere:
- Price
- Negotiated vehicle price
- Tax
- Sales tax (Price × rate)
- Fees
- Dealer fees and registration
- TradeInOwed
- Balance remaining on trade-in
- TradeInValue
- Value of trade-in vehicle
- DownPayment
- Cash down payment
- Rebate
- Manufacturer cash rebate
Example
$30,000 car + $1,800 tax (6%) + $1,000 fees − $5,000 down − $3,000 trade-in = $24,800 financed. At 7% for 60 months: monthly payment ≈ $491.
Step-by-Step Example
Suppose you are buying a $32,000 new car, putting $4,000 down, trading in a vehicle worth $8,000 with no negative equity, at 6.9% for 60 months, with $800 in fees and 7% sales tax.
- 1Monthly rate r = 6.9% ÷ 12 = 0.575% = 0.00575
- 2n = 60; (1.00575)^60 = 1.4116
- 3Monthly payment = $23,040 × (0.00575 × 1.4116) ÷ (1.4116 − 1)
- 4Payment = $23,040 × 0.008117 ÷ 0.4116 = $23,040 × 0.019722 = $454
- 5Total paid = $454 × 60 = $27,240
- 6Total interest = $27,240 − $23,040 = $4,200
Monthly payment: $454; total interest over 60 months: $4,200
Your true vehicle cost is $32,000 + $3,040 in tax and fees + $4,200 in interest = $39,240. If the dealer quotes a different monthly payment for the same loan amount and rate, ask them to itemize the difference before signing anything.
Understanding Your Results
The monthly payment is your fixed budget commitment for the next 3–6 years. Total interest reflects the borrowing cost on top of the purchase price. The equity schedule shows whether you are above or below water at any given point — critical if you need to sell the vehicle or file an insurance total-loss claim. New cars depreciate roughly 15–20% in year one, so buyers with small down payments and 60–72 month terms are often underwater for 12–24 months. The schedule tells you exactly when you cross into positive equity territory.
Factors That Affect Your Result
Loan Term and Depreciation Alignment
A 72 or 84-month term keeps payments low but extends the underwater period because depreciation outpaces principal paydown. For new vehicles, a 48-month term keeps equity close to market value throughout the loan.
Negative Equity on a Trade-In
Rolling negative equity from a previous loan into the new purchase adds that amount to the new principal. Trading in a vehicle with $5,000 in negative equity effectively increases your new loan by $5,000, extending the underwater period further.
Manufacturer vs. Third-Party Financing Rate
Manufacturers often offer 0% or sub-market rates on select models, but these deals may require forgoing a cash rebate of $1,500–$3,000. Calculate total cost under both the low rate and the rebate-plus-market-rate scenario.
Sales Tax Financing
Sales tax on vehicles ranges from 0% to 10%+ by state. On a $35,000 vehicle in a 9% tax state that is $3,150 added to the loan, and financing that amount at 7% for 60 months adds another $570 in interest on the tax itself.
GAP Insurance Cost and Source
GAP insurance covers the difference between loan balance and insurance payout if the car is totaled while underwater. It is valuable in early loan years on small down payments but should be purchased through an auto insurer, not financed through the dealer at $600–$1,200 markup.
Common Mistakes to Avoid
Negotiating Monthly Payment Instead of Purchase Price
Dealers are expert at structuring a lower monthly payment by extending the term or packaging add-ons invisibly. Always negotiate the out-the-door purchase price first, then separately negotiate financing terms.
Accepting Dealer Financing Without Competing Offers
Dealer financing often includes a rate markup of 1–2% above the lender's actual approval, with the dealer keeping the spread as profit. Getting a pre-approval from a bank or credit union before visiting gives you a rate ceiling to negotiate against.
Financing Dealer Add-Ons
Paint protection, rustproofing, and credit life insurance are high-margin items commonly bundled into the loan. Financing $2,000 in add-ons at 7% for 60 months costs $2,400 total — 20% more than their already-inflated cash price.
Choosing a Term Beyond 60 Months on a Used Vehicle
A 72-month loan on a 3-year-old used car means making payments on a 9-year-old vehicle. Repair costs spike on older vehicles, creating the scenario where you simultaneously carry a loan payment and large out-of-pocket repair bills.
Not Verifying Trade-In Value Independently
Dealers frequently undervalue trade-ins, particularly when negotiating a bundle that obscures the individual components. Check your vehicle's value on Kelley Blue Book, Edmunds, and CarMax before negotiating to have an independent reference.
Advanced Tips
Get Pre-Approved Before the Dealership
A pre-approval letter establishes a maximum rate and empowers you to evaluate dealer financing as a competing offer. Banks often match or beat dealer rates, and the offer creates real negotiating leverage on the financing terms.
Calculate True Cost of 0% vs. Cash Rebate
A $2,500 rebate applied to price reduction at 6.9% financing can cost less total than 0% financing on the full price. Run both scenarios in the calculator using actual loan amounts to identify the cheaper option for your specific situation.
Choose a Shorter Term When Rate Difference Is Small
If the rate spread between a 48-month and 72-month loan is under 0.5%, the 48-month term saves substantial interest and builds equity faster. The higher payment is often only $80–$120 more per month.
When to Consult a Professional
Consult a financial advisor before financing a vehicle if the monthly payment would push total debt payments above 40% of gross income, if you are considering an 84-month term, or if the vehicle price exceeds 50% of your annual income. A credit counselor can help if negative equity from previous trade-ins is compounding across multiple vehicle purchase cycles.
Authoritative Resources
External links are provided for informational purposes. FinCalc Pro does not endorse or have an affiliation with any third-party organizations listed below.
- Consumer Financial Protection Bureau
CFPB: Auto Loans
CFPB tools and guidance for understanding auto loan terms, dealer financing risks, and comparing offers.
- Federal Trade Commission
FTC: Buying a New Car
FTC consumer guidance on negotiating vehicle prices, understanding financing terms, and avoiding add-on fees.
- Consumer Financial Protection Bureau
CFPB: What Should I Know About Auto Loan Financing at a Dealership?
CFPB explanation of dealer financing markup, yo-yo financing, and how to protect yourself when financing through a dealer.
- Board of Governors of the Federal Reserve System
Federal Reserve: Consumer Credit G.19 (Auto Loan Rates)
Federal Reserve statistical release containing current and historical auto loan interest rate benchmarks.