Size and weight is a big decision factor when you are trying to find the ideal camera for your needs.
In this section, We are going to illustrate Olympus E-M10 IV and Canon M3 side-by-side from the front, back and top in their relative dimensions. Olympus E-M10 IV has external dimensions of 122 x 84 x 49 mm (4.8 x 3.31 x 1.93″) and weighs 383 g (0.84 lb / 13.51 oz) (including batteries). Canon M3 has external dimensions of 111 x 68 x 44 mm (4.37 x 2.68 x 1.73″) and weighs 366 g (0.81 lb / 12.91 oz) (including batteries).
Below you can see the front view size comparison of Olympus E-M10 IV and Canon M3. Canon M3 is clearly the smaller of the two cameras. Its body is 11mm narrower, 16mm shorter and 5mm thinner than Olympus E-M10 IV.
Here is the back view size comparison of Olympus E-M10 IV and Canon M3.
Now lets look at the top view comparison of Olympus E-M10 IV and Canon M3.
Weight is another important factor especially when deciding on a camera that you want to carry with you all day.
Canon M3 is 17g lighter than the Olympus E-M10 IV but we don't think this will make a significant difference.
Also keep in mind that body weight is not the only deciding factor when comparing two interchangeable camera bodies, you have to also take into account the lenses that you will be using with these bodies. Since Canon M3 has an APS-C sized sensor and Olympus E-M10 IV has a smaller Four Thirds sensor, Olympus E-M10 IV's lenses for a similar focal length and aperture will generally be lighter and smaller than the Canon M3 lenses.
Unfortunately neither Olympus OM-D E-M10 IV nor Canon EOS M3 provides any type of weather sealing in their body, so you have to give extra care especially when you are shooting outdoors. If weather sealing is a must-have feature for you, check these sections: Top Mirrorless Cameras with Weather Sealing
LCD Screen Size and Features
Olympus E-M10 IV and Canon M3's LCD screens has the same diagonal size of 3".
Both cameras feature Tilting screens
where you can change the angle of the screen to make it easier to shoot from waist or over the head levels.