One car garage size

Answer 1

on a slab of concrete 12'x24' is about the standard for full-size trucks and suv's and older American cars i.e. Cadillac, Lincoln, Olds and Chrysler all had model years where they measured 18' on length. Two Car adage double the width plus 16" for the slab.

Don't forget the footing at the perimeter and steel plus forms when estimating slab costs and materials.