Below you can see the front view size comparison of Canon M100 and Nikon D5300. Canon M100 is clearly the smaller of the two cameras. Its body is 17mm narrower, 31mm shorter and 41mm thinner than Nikon D5300.
Canon M100 vs Nikon D5300 - Front View
Canon M100 vs Nikon D5300 - 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