How this auto loan calculator works
We use the standard fixed-rate amortization formula. Your monthly payment is sized so that the loan balance reaches zero at the end of the term. Early on, most of each payment is interest because the balance is still large; as the balance shrinks, more of each payment goes to principal.
- Amount financed = vehicle price − down payment − trade-in value.
- Payment formula: M = P × [ r(1+r)n / ((1+r)n − 1) ], with r = APR / 12 and n = term in months.
- An extra monthly payment is applied straight to principal, which both shortens the term and lowers total interest.
- 0% APR promos amortize linearly: monthly payment is just amount financed divided by the term in months.
Example
On a $35,000 vehicle with $5,000 down and 6.5% APR over 60 months, the payment is about $587/mo and you pay roughly $5,200 in interest over the life of the loan. Adding $100/mo extra clears the loan about 9 months early and saves roughly $850 in interest. The exact figures update as you edit the inputs above.
Tips
- Compare 60 vs 72 months at the same APR to see the interest cost of a longer term.
- A bigger down payment cuts both the payment and the interest you ever pay.
- Even $50/mo extra hits a meaningful share of the original interest bill on a 5-year loan.
What's not included
- Sales tax, title, registration, and dealer fees vary by state and dealer.
- Gap insurance, extended warranties, and other add-ons.
- Negative equity on a trade-in (you owe more on the old car than it's worth). Subtract the rollover from the trade-in field to approximate it.
Frequently asked questions
Is a 72-month loan a bad idea?
A longer term lowers the monthly payment but raises total interest, and you spend more time underwater (owing more than the car is worth). It can be fine if you intend to keep the car for the full term and the rate is competitive. Compare 60 vs 72 months above to see the trade-off in dollars.
How does my credit score affect the APR?
Most lenders price auto loans in tiers by FICO score. A score in the high 700s typically qualifies for the advertised promo rate; below the mid-600s rates can be several points higher. Get a pre-approval from your bank or credit union before you walk into the dealership.
Should I take the 0% APR or the cash rebate?
Run both: set APR to 0 with the original price, then to your bank's rate with the rebate subtracted from the vehicle price. The lower total paid (over the term you actually plan to hold the loan) is the better deal.
Does this include sales tax and fees?
No. Sales tax, title, registration, and dealer fees vary too much by state and dealer to include by default. If your lender rolls them into the loan, add them to the vehicle price field.
See also the mortgage calculator and methodology & sources.