Approximate outside measurements of Model 3?
the size of a BMW 3 Series
Google (via the M3 wiki) says....
Length, 4,676 mm (184.1 in) est. Width, 1,885 mm (74.2 in) est. Height, 1,435 mm (56.5 in) est.
So having just Googled the dimensions of the car parked where my M3 will park, the M3 is slightly larger, but will still fit without having to get rid of more junk from the garage. Not that we shouldn't get rid of that junk anyway.