This is how I figured it out. Someone told me to use this as a rule of thumb. Cut the price of the car in half and then divide over how many months. Example..
Car stickers for 25k, cut in half to 12.5k. Divide over 36 or 48 months.
36=347.22
48=260.42
That should give you a good idea on how much to pay per month.

 

Then tack on the $2k leasing fee and don't forget tax.