Auto Payment Comparison Calculator View Calculator Calculate and compare (formatted side by side) the payment amounts for up to 4 auto loans. Use this calculator to help compare interest rates or see the effect of putting more money as a down payment. This calculator is also good for comparing lower-interest deals with cash back offers. ("Should I take the cash rebate and get a loan with a higher interest rate?") You can also see quickly what happens if you apply your trade-in and/or dealer rebate to the down payment or pocket it for something else. Learn more about putting this calculator or other calculators on your website.