While it would depend on the size of the cars, going on the width of the average sedan, you will likely need one that is at least 18' wide if you are looking to park them side by side. I would suggest the ShelterLogic 18 x 30 Super Max Commercial Grade 12 Leg Canopy Shelter - 26767. Of course, you will want to measure your cars to make sure this will be the appropriate shelter.