Auto Loan True Cost Calculator

How dealer payment shopping creates friction

Monthly payment quotes can hide term length, backend products, and fees rolled into amount financed. Lengthening term lowers the payment while usually raising total interest.

True-cost math recovers the deal from price, tax, fees, down payment, APR, and term — then scores interest dollars, not just the payment dial.

How to use this calculator

Lock an out-the-door style price when you can, then enter tax %, fees, down payment, APR, and term. Recompute whenever the desk adds a warranty or extends months to “hit a payment.”

Compare a short term and a long term side by side. The payment gap is obvious; the interest gap is the friction story.

Worked example

Vehicle price $28,000, 8% tax, $1,200 fees, $4,000 down → amount financed ≈ $28,000 + $2,240 + $1,200 − $4,000 = $27,440.

At 7.5% APR for 60 months, payment and total interest differ materially from the same amount financed at 72 or 84 months. Stretching term to “afford” the car is often how total interest quietly climbs into four figures of extra friction.

Financing a $1,800 extended warranty into the note raises amount financed and interest paid even if the warranty is optional. Price add-ons in cash terms before agreeing to roll them in.

Tax and fees

Sales tax treatment varies by state and trade-in rules. Adjust the tax % to your quote — California district taxes and Texas/Florida local patterns are not identical.

Negative equity from a prior loan is not auto-modeled; rolling it in increases amount financed and should be entered as a higher financed total.

Assumptions

• Fixed APR and level amortizing payments.
• Tax and fees applied as you enter them to build amount financed.
• Down payment reduces financed amount dollar-for-dollar in the simplified model.
• No negative equity, balloon, or lease comparison built in.
• Not a dealer offer, GAP/warranty recommendation, or credit decision.

Related guides

Deeper explainers that sit behind this calculator’s math:

• APR vs Interest Rate: Why Your Monthly Payment Is Not the Whole Cost — A plain-English US guide to APR, fees, and total interest — for personal loans and revolving credit.
• The Auto Loan APR Trap: Payment Shopping vs Total Cost — How dealers frame monthly payments — and how to recover amount financed, APR, and total interest.