EPA does interior volume to determine car size. My 1987 LaBaron coupe was midsize. The convertible version was compact. In the olden times, exterior dimensions were used to determine size. My first new Mopar was a midsize 1967 Plymouth Bevedere 2 door hard top. The convertible was midsize, too. That gem made me stuck on Mopar. BTW. The midsize Belvedere was 200" long, 76.5" wide with a 116" wheelbase. Petty won 10 consecutive NASCAR races with this body. I was stuck on NASCAR. Today? I don't bother.