What is negative equity on a trade-in?

If you owe $15,000 on your current car but it's only worth $12,000, you have $3,000 in negative equity. Dealers typically "roll" this into your new loan, meaning you're financing more than the new car costs. It's sometimes called being "upside down" or "underwater."

How do sales tax and title/registration fees affect my loan?

In most US states, sales tax applies only to price minus trade-in value. Title and registration fees and dealer doc fees vary widely by state and dealer, and they all get added to your loan amount. A few states (like California and Virginia) do not offer the trade-in tax credit — use the trade-in tax credit field and check your state revenue department.

What is a good APR for a car loan?

It depends mostly on your credit score and whether the car is new or used. For reference, Experian reported average APRs of about 6.7% for new and 11.9% for used vehicles in Q1 2025, with borrowers at the top of the credit range paying far less than average and subprime borrowers paying far more. Credit unions and online lenders can beat dealership financing, so check rates from at least 3 lenders before signing — the difference can save thousands over the life of the loan.

Is a 72-month or 84-month car loan a bad idea?

Long-term loans of 72 or 84 months have three major risks. First, you pay dramatically more in total interest — a $35,000 loan at 8% over 84 months costs about $10,800 in interest vs. about $7,600 over 60 months. Second, you will be underwater (owing more than the car is worth) for most of the loan term because cars depreciate faster than long-term loans amortize. Third, you are more likely to need GAP insurance, which adds cost. If you need a 72 or 84-month loan to afford the monthly payment, the car is probably too expensive for your budget. Stick to 48 to 60 months whenever possible.

Should I get pre-approved before visiting the dealership?

Yes, absolutely. A pre-approval from your bank or credit union gives you three advantages: it sets a firm budget before you walk into the showroom, it gives you a rate benchmark to compare against dealer financing offers, and it prevents the dealer from marking up your interest rate (a practice called dealer reserve where the dealer adds 1% to 2% to your approved rate and keeps the difference). Many credit unions offer same-day pre-approvals online. Bring your pre-approval letter to the dealership and only share it after you have negotiated the out-the-door price.

What is GAP insurance and do I need it?

GAP (Guaranteed Asset Protection) insurance covers the difference between your loan balance and the car's actual cash value if it's totaled or stolen. You should strongly consider GAP if you put less than 20% down, finance for 72+ months, or roll negative equity into the loan — because you'll be underwater for most of the loan term. However, compare GAP quotes from your auto insurer (often added to your policy for a small annual cost) against the dealer finance office, where it is usually a much larger one-time fee. Some insurers and credit unions include GAP-like coverage as a standard policy feature.

Auto Loan Calculator

Calculate monthly car payments with trade-in value, negative equity rollover, sales tax, and dealer fees. See total interest and out-the-door price.

✓ Tested formula & cited sources Checked against independent sources · Oct 12, 2026 Private: runs in your browser

Vehicle Price

Agreed purchase price before any deductions

Loan Term

Longer terms mean lower payments but more interest

Annual Interest Rate (APR)(%)

Your loan APR based on credit score and lender

Cash Down Payment

Cash you pay at signing

Trade-In Value

Dealer's offer for your trade-in vehicle

Amount Owed on Trade-In

Remaining loan balance on your trade-in. If trade-in value < amount owed = negative equity, which is added to your new loan.

Sales Tax Rate(%)

In most states, sales tax applies to (Vehicle Price − Trade-In Value) — see the next field for states that do not.

Does Your State Tax Credit the Trade-In?

Most states tax only the price after the trade-in value. A few (California and Virginia among them) tax the full price — check your state.

Title, Registration & Doc Fees

Flat fees charged by DMV and dealership (title, registration, doc fee). Typically $300–$800.

Results

Estimated Monthly Payment

$914.46

Over the loan you'll pay $3,260.53 in interest on top of the amount financed — a shorter term or larger down payment cuts that fast. Cars depreciate quickly in the first few years, so a long loan term risks owing more than the car is worth (being "underwater") if you need to sell or trade in early.

Out-the-Door Price (Before Financing): $37,660.00
Total Amount Financed: $29,660.00
Total Interest Paid: $3,260.53
Total Cost of Vehicle (All-In): $40,920.53
Sales Tax (8% on $27,000.00 — price minus trade-in value): $2,160.00
Title, Registration & Doc Fees: $500.00

Making a decision? The real monthly cost, the 20/4/10 guideline, your debt-to-income and the cash you need at signing. Can I afford this car? →

The formula

M = P × [r(1+r)^n] / [(1+r)^n − 1] | Taxable = Price − Trade-In Value

P, r & n: Loan Terms (Principal, Rate, Months)
Negative Equity: Underwater Trade-In

Worked example — Vehicle Price 35000, Annual Interest Rate (APR) 6.9 %, Cash Down Payment 5000, Trade-In Value 8000

Estimated Monthly Payment = $914.46

Full explanation ↓

How Auto Loan Calculator Works

M = P × [r(1+r)^n] / [(1+r)^n − 1] | Taxable = Price − Trade-In Value

The monthly payment uses the standard loan amortization formula where M equals the monthly payment, P is the amount financed, r is the monthly interest rate (APR divided by 12), and n is the loan term in months. The formula M = P x [r(1+r)^n] / [(1+r)^n - 1] calculates a fixed payment that fully repays the loan over the term. The amount financed is calculated as: Vehicle Price plus Sales Tax plus Title and Registration Fees, minus Down Payment, minus Trade-In Value, plus any Negative Equity (when the trade-in loan balance exceeds the trade-in value).

Sales tax is applied to the vehicle price minus the trade-in value (the allowance, even when the trade-in is not paid off), following the most common US state tax rule; you can switch this off for states that tax the full price. The total cost of the loan includes all interest paid over the full term, which increases significantly with longer loan terms.

P, r & n: Loan Terms (Principal, Rate, Months) — Principal = Price + Tax + Fees + Negative Equity − Down − Trade-In. Monthly rate r = APR ÷ 12. Term n in months (typical: 36-84). These three values determine your monthly payment through the standard amortization formula.
Negative Equity: Underwater Trade-In — When you owe more on your trade-in than it's worth, the difference is added to your new loan principal.

Auto loan breakdown — vehicle price minus down payment equals financed amount

Worked Examples

Marcus is buying a used Honda CR-V priced at $28,000. He has $5,000 cash down, a trade-in worth $8,000 with no remaining loan, lives in a state with 7% sales tax, and expects $400 in title and doc fees. The dealer offers 6.9% APR for 60 months. What is his real monthly payment?

vehiclePrice = 28000 · loanTerm = 60 · interestRate = 6.9 · downPayment = 5000 · tradeInValue = 8000 · tradeInOwed = 0 · salesTaxPct = 7 · titleRegFees = 400

$331.87/month — $3,112.08 total interest over 60 months

With $8,000 positive trade-in equity: taxable amount is $28,000 - $8,000 = $20,000 at 7% tax = $1,400. Out-the-door price = $28,000 + $1,400 + $400 = $29,800. Amount financed = $29,800 - $5,000 - $8,000 = $16,800. Monthly payment at 6.9% over 60 months: approximately $331.87. Total interest paid: about $3,112. Marcus saves significantly by having a paid-off trade-in: the $8,000 trade-in both reduces the amount financed and reduces the taxable amount.

Jasmine wants a new SUV priced at $42,000. She has only $2,000 down, her trade-in is worth $15,000 but she still owes $18,000 on it, and her state charges 6% sales tax with $600 in fees. The dealer offers 8.5% APR for 72 months. What will her payments look like?

vehiclePrice = 42000 · loanTerm = 72 · interestRate = 8.5 · downPayment = 2000 · tradeInValue = 15000 · tradeInOwed = 18000 · salesTaxPct = 6 · titleRegFees = 600

$803.94/month — $12,663.58 total interest over 72 months

Negative equity: the $15,000 trade-in value is $3,000 less than the $18,000 payoff, so that $3,000 is rolled into the new loan. The trade-in value still counts as a tax credit in most states, so the taxable amount is $42,000 - $15,000 = $27,000 at 6% = $1,620. Out-the-door = $42,000 + $1,620 + $600 = $44,220. Amount financed = $44,220 + $3,000 (negative equity) - $2,000 (down) = $45,220. Monthly payment at 8.5% over 72 months: approximately $803.94. Total interest: about $12,664 — the underwater trade-in and long loan term make this a very expensive deal.

Understanding the Result

An auto loan is one of the largest financial commitments most people make outside of a mortgage, yet few buyers understand how the numbers actually work at the dealership. Auto financing at scale dates back to 1919, when General Motors founded GMAC (General Motors Acceptance Corporation) to help customers afford cars. Today the auto loan market is enormous: U.S. households owe well over $1 trillion in auto loan debt (Federal Reserve Bank of New York), and recent Experian data put the average new-vehicle loan above $40,000.

Most online auto loan calculators miss the details that actually matter at the dealership. This one correctly handles negative equity (when your trade-in is underwater — you owe more than it is worth), applies sales tax only to the taxable amount as most states require, and includes the title, registration, and doc fees that push your actual loan higher. Longer loan terms of 72 to 84 months dramatically increase total interest and create a high risk of negative equity on your next trade-in.

Understanding the full picture — out-the-door price, amount financed, and total loan cost — is the best defense against dealer add-ons and unfavorable financing. Always negotiate the out-the-door price, not the monthly payment, and secure financing pre-approval from a credit union or bank before visiting the dealership.

How to Use

Enter the agreed vehicle price.
Select your loan term and enter your APR.
Enter your cash down payment, trade-in value, and any remaining loan balance on the trade-in.
Add your local sales tax rate and any title/registration/doc fees.
The calculator applies sales tax only to (price − trade-in value), as most states require.

Quick Reference

Down Payment Target	20% of vehicle price
Max Recommended Term	48-60 months
Avg New-Car APR (Experian, Q1 2025)	≈ 6.7%
Avg Used-Car APR (Experian, Q1 2025)	≈ 11.9%
Sales Tax Basis	Price minus Trade-In (most states)
Doc Fee	Varies by state and dealer — ask for it in writing
Key Metric	Total cost, not monthly payment

Frequently Asked Questions

What is negative equity on a trade-in?: If you owe $15,000 on your current car but it's only worth $12,000, you have $3,000 in negative equity. Dealers typically "roll" this into your new loan, meaning you're financing more than the new car costs. It's sometimes called being "upside down" or "underwater."
How do sales tax and title/registration fees affect my loan?: In most US states, sales tax applies only to price minus trade-in value. Title and registration fees and dealer doc fees vary widely by state and dealer, and they all get added to your loan amount. A few states (like California and Virginia) do not offer the trade-in tax credit — use the trade-in tax credit field and check your state revenue department.
What is a good APR for a car loan?: It depends mostly on your credit score and whether the car is new or used. For reference, Experian reported average APRs of about 6.7% for new and 11.9% for used vehicles in Q1 2025, with borrowers at the top of the credit range paying far less than average and subprime borrowers paying far more. Credit unions and online lenders can beat dealership financing, so check rates from at least 3 lenders before signing — the difference can save thousands over the life of the loan.
Is a 72-month or 84-month car loan a bad idea?: Long-term loans of 72 or 84 months have three major risks. First, you pay dramatically more in total interest — a $35,000 loan at 8% over 84 months costs about $10,800 in interest vs. about $7,600 over 60 months. Second, you will be underwater (owing more than the car is worth) for most of the loan term because cars depreciate faster than long-term loans amortize. Third, you are more likely to need GAP insurance, which adds cost. If you need a 72 or 84-month loan to afford the monthly payment, the car is probably too expensive for your budget. Stick to 48 to 60 months whenever possible.
Should I get pre-approved before visiting the dealership?: Yes, absolutely. A pre-approval from your bank or credit union gives you three advantages: it sets a firm budget before you walk into the showroom, it gives you a rate benchmark to compare against dealer financing offers, and it prevents the dealer from marking up your interest rate (a practice called dealer reserve where the dealer adds 1% to 2% to your approved rate and keeps the difference). Many credit unions offer same-day pre-approvals online. Bring your pre-approval letter to the dealership and only share it after you have negotiated the out-the-door price.
What is GAP insurance and do I need it?: GAP (Guaranteed Asset Protection) insurance covers the difference between your loan balance and the car's actual cash value if it's totaled or stolen. You should strongly consider GAP if you put less than 20% down, finance for 72+ months, or roll negative equity into the loan — because you'll be underwater for most of the loan term. However, compare GAP quotes from your auto insurer (often added to your policy for a small annual cost) against the dealer finance office, where it is usually a much larger one-time fee. Some insurers and credit unions include GAP-like coverage as a standard policy feature.

Common Uses

•Comparing loan offers from dealerships, banks, and credit unions to find the best interest rate and monthly payment
•Budgeting for a new or used car purchase by estimating monthly payments before visiting a dealer
•Deciding between different loan terms (36 vs 60 vs 72 months) to balance payment affordability against total interest cost
•Evaluating the impact of down payment size, trade-in value, and sales tax on the total financed amount

Pro Tips

→Always negotiate the out-the-door price first, not the monthly payment. Dealers can lower monthly payments by stretching the loan term, which costs you thousands more in interest.
→Get financing pre-approved from your bank or credit union before visiting the dealership. This gives you a baseline rate to compare against dealer financing — and the dealer may beat it to earn your financing business.
→The 20/4/10 rule of thumb for affordable car buying: put 20% down, finance for no more than 4 years (48 months), and keep total monthly vehicle expenses (payment + insurance + fuel) under 10% of gross monthly income.
→Avoid rolling negative equity into a new loan whenever possible. If you are underwater on your current car, consider paying down the difference in cash rather than financing it at 7-10% APR over 5-7 years.
→Be skeptical of 72-month and 84-month loans. While they lower monthly payments, you will be underwater on the car for most of the loan term and pay dramatically more in total interest — often thousands more.
→Watch for dealer add-ons in the finance office: extended warranties, GAP insurance (often cheaper through your own insurer), VIN etching, fabric protection, and nitrogen tire fills are all high-margin items you can decline or buy elsewhere for less.

Limitations to Know

•This calculator uses the standard amortization formula with a fixed APR, but dealer financing may involve simple interest loans that calculate interest daily rather than monthly.
•It does not account for manufacturer incentives, rebates, or special financing offers (0% APR) that may be available on new cars. Lease buyout calculations are not supported.
•Credit score impact on APR is not modeled — actual rates vary significantly by credit tier. Insurance costs, GAP insurance, and extended warranties are not included but can add $50-$200+ to monthly ownership costs.
•The sales tax calculation follows the most common US method (tax on price minus trade-in); a few states, including California and Virginia, give no trade-in credit and tax the full purchase price (set the trade-in tax credit field to No), and some states cap the credit. Check your state rules.

Sources

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TheCalcUniverse. "Auto Loan Calculator — Payment, Trade-In & Negative Equity." TheCalcUniverse, 2026, https://thecalcuniverse.com/automotive/auto-loan-calculator/. Accessed October 25, 2026.

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