By Meraj Uddin Provat · Last reviewed May 23, 2026 · Editorial Standards
The sticker price is never what you finance. By the time sales tax, title and registration fees, and any negative equity from your trade-in get rolled in — minus your down payment and trade — the real loan can be thousands more than the price on the window. This calculator builds the actual monthly payment from all of it.
Auto Loan Calculator
Your real monthly car payment — including tax, trade-in, and fees rolled into the loan. Updates as you type.
Sales tax is applied to price minus trade-in in most states (a few tax the full price). Negative equity from the old loan is rolled into the new one. Estimates only — confirm your state’s tax treatment and lender terms. Not a loan offer or financial advice.
How to use this calculator
Enter the vehicle price, your down payment, and trade-in details (including anything you still owe on the trade — that’s the part dealers gloss over). Add your rate, term, sales-tax rate, and the title/registration/doc fees. The result is your true monthly payment plus a full breakdown of what you’re actually financing.
What actually gets financed
Your loan is rarely just “price minus down.” It’s:
`price − down payment − trade-in equity + sales tax + fees + any negative equity`
- Sales tax — in most states, applied to price minus trade-in (a few tax the full price). On a $35,000 car at 6% that’s ~$2,000 financed.
- Title, registration, doc fees — a few hundred dollars, almost always rolled in.
- Negative equity — if you owe more on your trade-in than it’s worth, the difference is added to the new loan. This is the silent budget-killer.
The negative-equity trap
If you owe $18,000 on a trade-in worth $14,000, you’re $4,000 underwater. Roll that into a new loan and you’re paying interest on a car you no longer own. The calculator flags this explicitly because it’s the single most common reason buyers end up deeper underwater every trade cycle. If you can pay off negative equity in cash instead of financing it, do.
Why loan term matters more than the rate
Dealers sell the monthly payment, so they stretch the term. Watch what 84 months does:
| Term | Payment (≈$30k financed @ 7.5%) | Total interest |
|---|---|---|
| 36 months | ≈ $933 | ≈ $3,580 |
| 60 months | ≈ $601 | ≈ $6,070 |
| 84 months | ≈ $461 | ≈ $8,720 |
The 84-month payment looks great and costs ~$5,000 more in interest — and you’re likely underwater for most of the loan because cars depreciate faster than a long loan pays down. Pick the shortest term whose payment you can afford, not the longest one that “fits.”
How to lower the real payment
- Bigger down payment — directly shrinks what’s financed and helps you stay right-side-up.
- Shorter term — far less total interest; the calculator shows the trade-off.
- Kill negative equity separately — don’t roll an old underwater loan into a new one if you can avoid it.
- Shop the rate — a credit-union pre-approval often beats dealer financing; even 1% matters over 60 months.
- Negotiate price, not payment — agree on the out-the-door price first; “what monthly works for you?” is how term and rate get inflated.
Frequently asked questions
Is sales tax based on the full price or after trade-in? Most states tax price minus trade-in (a real savings). A handful tax the full price. Set the rate to your state and note your local rule.
Should I roll fees into the loan? You can, but you pay interest on them for the whole term. Paying fees in cash is cheaper if you can.
What’s a good auto loan term? 36–60 months for most buyers. 72–84 months minimizes the payment but maximizes interest and the time you spend underwater.
Does a trade-in lower my taxes? In most states, yes — sales tax is calculated on the price after the trade-in credit, which can save hundreds.
What is negative equity / being “underwater”? Owing more on the car than it’s worth. Rolling it into a new loan compounds the problem — you finance debt on a car you don’t have anymore.
Should I get financing before going to the dealer? Usually yes. A bank or credit-union pre-approval gives you a rate to beat and removes the dealer’s incentive to inflate the financing.
How much car can I afford? A common guideline: total transportation costs under ~15–20% of take-home pay, with a down payment of 10–20%. Run the payment here, then sanity-check it against your budget.
Methodology
The amount financed is vehicle price minus down payment and trade-in equity, plus sales tax (applied to price minus trade-in by default), title/registration/doc fees, and any negative equity from the trade. The monthly payment uses the standard fixed-rate amortization formula. Total cost is all payments plus the down payment. State tax treatment varies — verify your local rule. Estimates for planning only; not a loan offer or financial advice.
Written by the CalcCottage team. We show the real number, not the marketing number.