The size of the lug wrench varies according to the size and type of car you own. Depending on the vehicle, the nuts can either be metric or standard. Here the most common sizes are 10 to 14 mm or 7/16 to 5/8 inches. While buying a lug wrench for your car, make sure that your tire iron fits them well. You can take help from the owner’s manual that comes with the car to know the appropriate size. Otherwise, consult an expert or read the customer review section to have a clear idea.