Bankrate.com has a couple of different auto loan calculators they allow their users to access. Cars.com also has a free loan calculator that offers a few different features from Bankrate, and Autoloancalculator.com has an online loan calculator.
Bankrate has two separate loan calculators that are both free to use but have different features. The calculator that isn't labeled free, but is free to use, allows for more in-depth research into how much the loan is going to be decades from now and even gives an amortization schedule. Cars.com has a number of different tabs so users can calculate a car loan and also determine whether or not the loan is affordable.