Below you can see the front view size comparison of Canon M3 and Canon M6. Canon M3 is 1mm narrower and 1mm thinner than Canon M3 but they have the same height of 68mm.
Canon M3 vs Canon M6 - Front View
Canon M3 vs Canon M6 - Top View
The chart below depicts how two cameras compare with average dimensions of the cameras in their class.
Camera Size Comparison
Select Two Cameras for Size Comparison