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 Nikon P510 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). Nikon P510 has external dimensions of 120 x 83 x 102 mm (4.72 x 3.27 x 4.02″) and weighs 555 g (1.22 lb / 19.58 oz) (including batteries).
Below you can see the front view size comparison of Olympus E-M10 IV and Nikon P510. Nikon P510 is 2mm narrower and 1mm shorter than Olympus E-M10 IV but it is also 53mm thicker. As you can tell, actually this is not a fair size comparison since Nikon P510 has a built-in lens but Olympus E-M10 IV doesn't. Once you put a lens on E-M10 IV, its thickness will increase significantly.
Here is the back view size comparison of Olympus E-M10 IV and Nikon P510.
Now lets look at the top view comparison of Olympus E-M10 IV and Nikon P510.
Weight is another important factor especially when deciding on a camera that you want to carry with you all day.
Olympus E-M10 IV is significantly lighter (172g ) than the Nikon P510 which may become a big advantage especially on long walking trips.
Again, this comparison may not be very useful in real life as we are comparing the weight of a camera with a built-in lens to the body-only weight of an interchangeable lens camera. Once you put a lens on E-M10 IV, the total kit will weigh much higher.
Unfortunately neither Olympus OM-D E-M10 IV nor Nikon Coolpix P510 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 Top Bridge Cameras with Weather Sealing
LCD Screen Size and Features
Olympus E-M10 IV and Nikon P510's LCD screens has the same diagonal size of 3.00".
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.