Auto Loan Calculator with Trade-In and Sales Tax
Estimate the true monthly cost of a car after down payment, trade-in credit, sales tax, and dealer fees. See total interest paid and how a shorter term or larger down payment changes the picture.
Inputs
Results
- Monthly payment
- $636.00
- Amount financed
- $31,740.00
- Sales tax
- $2,240.00
- Total interest
- $6,420.27
- Total cost of vehicle
- $41,160.27
Includes inputs, results, and schedule.
Payment schedule
| Year | Principal | Interest | Balance |
|---|---|---|---|
| 1 | $5,435.89 | $2,196.16 | $26,304.11 |
| 2 | $5,857.89 | $1,774.16 | $20,446.22 |
| 3 | $6,312.66 | $1,319.40 | $14,133.56 |
| 4 | $6,802.72 | $829.33 | $7,330.84 |
| 5 | $7,330.84 | $301.22 | $0.00 |
Auto loan formula
The monthly car payment uses the same amortization formula as a mortgage. Because auto loans are typically 3–7 years, small changes in APR make a meaningful difference in total interest — a 1% higher rate on a 5-year, $30,000 loan adds roughly $800 in interest.
Down payment guidance
A 20% down payment on a new car (10% used) helps you avoid negative equity — owing more than the car is worth after depreciation. This calculator makes it easy to see how a bigger down payment shrinks both the monthly payment and total interest.
Frequently asked questions
Does the calculator handle a negative-equity trade-in?
Yes — enter the trade-in value and how much you still owe. The remaining balance rolls into the amount financed.
Is sales tax charged on the trade-in?
Most U.S. states tax only the difference between the vehicle price and trade-in value. This calculator uses that rule.
What is a good auto loan APR?
Excellent credit typically qualifies for the lowest advertised rates; sub-prime rates can be several points higher. Always compare offers from a credit union alongside dealer financing.