Canon M3 weighs 366 g (0.81 lb / 12.91 oz) and has external dimensions of 111 x 68 x 44 mm (4.37 x 2.68 x 1.73″). Considering that the average weight of Mirrorless type cameras is 437g, Canon M3 is a remarkably light camera for its class. With a thickness of 44mm, it has an average thickness for its class.
Here is the front and top view image of Canon M3 with the dimensions:
In order to give you a better idea about the real life size of Canon M3, we have added an image of how it looks next to a credit card and an AA type battery.
Now lets compare the weight and thickness of Canon M3 with its main competitors:
Canon M3 doesn't have any environmental sealings on its body so you got to be extra careful to protect it against water and dust. If you shoot under these conditions very often, consider checking Top Mirrorless Cameras with Weather Sealing page.