Auto Loan Calculator
Estimate your monthly auto loan payment, total interest, and total sales tax — factoring in a trade-in, down payment, and your local sales tax rate.
How It's Calculated
Formula
\text{Payment} = \dfrac{P \cdot r (1+r)^n}{(1+r)^n - 1}, \quad P = \text{Price} - \text{Trade-in} - \text{Down Payment} + \text{Sales Tax}This calculator estimates your monthly auto loan payment from the vehicle price, an optional trade-in and down payment, your loan term and interest rate, and your local sales tax rate. It finances the vehicle price minus your trade-in and down payment, plus sales tax, using the standard fixed-rate loan amortization formula (the same formula used for mortgages and personal loans). Monthly payments only. Important assumption: this calculator assumes your trade-in value reduces the taxable vehicle price before sales tax is applied. That credit isn't universal — some states tax the full vehicle price regardless of trade-in. Enter your local sales tax rate and treat the tax figure here as an estimate, not a filing-accurate number. This calculator does not use a state-by-state tax database; it applies the one rate you enter, the same way in every case.
Worked Examples
Example: with a trade-in
- Vehicle price: $28,000
- Trade-in value: $6,000
- Down payment: $2,000
- Sales tax rate: 6%
- Taxable vehicle amount = $28,000 − $6,000 = $22,000
- Sales tax = $22,000 × 6% = $1,320
- Financed principal = $28,000 − $6,000 − $2,000 + $1,320 = $21,320
- At 6.5% APR over 5 years (60 monthly payments), the monthly payment is $417.15
Example: no trade-in (same vehicle, same tax rate)
- Vehicle price: $28,000
- Trade-in value: $0
- Down payment: $2,000
- Sales tax rate: 6%
- Taxable vehicle amount = $28,000 − $0 = $28,000
- Sales tax = $28,000 × 6% = $1,680
- Financed principal = $28,000 − $0 − $2,000 + $1,680 = $27,680
- At the same 6.5% APR over 5 years, the monthly payment is $541.59
- Without the trade-in, both the taxable amount and the financed principal are higher — this is the trade-in tax-credit assumption's concrete effect on the result.
Frequently Asked Questions
Does this account for my state's trade-in tax rules?
No — tax treatment varies by state and locality. This calculator assumes your trade-in value reduces the taxable vehicle price, then applies the one sales tax rate you enter. Some states don't allow a trade-in tax credit at all; check your local rules for an exact figure. This is a deliberate, disclosed simplification, not a state-by-state tax database.
Does this calculator finance title, registration, or other fees?
No. Only the vehicle price (minus trade-in and down payment, plus the sales tax computed above) is financed. Title, registration, and other dealer fees are not included.
What if I owe money on my trade-in vehicle?
This calculator doesn't model negative equity (an amount still owed on a trade-in). Enter your trade-in's actual value as credited by the dealer; if you owe more than it's worth, your real financed amount will be higher than what this calculator shows.
Why does the total loan cost not include my down payment?
Total loan cost here is the total of everything paid to the lender over the life of the loan — the financed principal plus total interest. Your down payment is paid upfront in cash and isn't part of what you finance, so it isn't included in this figure.
Can I choose a payment frequency other than monthly?
Not in this version — this Auto Loan Calculator supports monthly payments only. A frequency selector (like the general-purpose Loan Calculator's) isn't available here yet.