Free online auto loan calculator

How to use

1. Enter the vehicle price, down payment, trade-in value, sales tax %, and any fees.
2. Set the APR (from your lender) and loan term in months.
3. Optionally add an extra monthly payment to see interest savings.
4. The calculator shows the net loan amount, monthly payment, and total interest.
5. Press “Show schedule” for the full month-by-month amortization table.

Formula

The loan amount is built up in two steps, and the monthly payment uses the standard amortization formula.

Loan amount:

Taxable base = price − down payment − trade-in
Sales tax    = taxable base × (tax% / 100)
Loan amount  = taxable base + sales tax + fees

Monthly payment:

M = L × r(1 + r)ⁿ / ((1 + r)ⁿ − 1)

Where L is the loan amount, r is the monthly rate (APR ÷ 12 ÷ 100), and n is the term in months.

Worked example

Vehicle: $35,000 | Down: $5,000 | Trade-in: $0 | Tax: 8% | Fees: $500 | Rate: 6.5% APR | Term: 60 months

• Taxable base: $35,000 − $5,000 = $30,000
• Sales tax: $30,000 × 0.08 = $2,400
• Loan amount: $30,000 + $2,400 + $500 = $32,900
• Monthly rate: 6.5 ÷ 12 ÷ 100 ≈ 0.005417
• Monthly payment: ≈ $643/month
• Total interest: ≈ $5,580
• Total cost of the car: price + $500 fees + $5,580 interest = $41,080 (versus the $35,000 sticker).

Notes

• APR vs. dealer rate — dealers often markup the lender’s rate by 1–3%. Get a quote from your bank or credit union first and use it as your negotiating floor.
• Trade-in cuts both loan and tax — in most U.S. states the trade-in value reduces the taxable base before sales tax is applied, so the savings are bigger than just the principal cut. A few states don’t allow this; check local rules.
• Term length is a trap — a 72- or 84-month loan lowers the monthly payment but dramatically increases total interest and the window where you owe more than the car is worth (“underwater”).
• Not included: GAP insurance, extended warranties, and dealer add-ons. These roll into the loan silently and can add 5–15% to the total paid. Decline them unless you’ve priced them separately.
• Extra monthly payments go straight to principal and can shave months off a typical auto loan for the price of one skipped coffee a day.