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 Canon T7i and Nikon D3400 side-by-side from the front, back and top in their relative dimensions. Canon T7i has external dimensions of 131 x 100 x 76 mm (5.16 x 3.94 x 2.99″) and weighs 532 g (1.17 lb / 18.77 oz) (including batteries). Nikon D3400 has external dimensions of 124 x 98 x 76 mm (4.88 x 3.86 x 2.99″) and weighs 395 g (0.87 lb / 13.93 oz) (including batteries).
Below you can see the front view size comparison of Canon T7i and Nikon D3400. Nikon D3400 is 7mm narrower and 2mm shorter than Canon T7i but they have the same thickness of 76mm.
Here is the back view size comparison of Canon T7i and Nikon D3400.
Now lets look at the top view comparison of Canon T7i and Nikon D3400.
Weight is another important factor especially when deciding on a camera that you want to carry with you all day.
Nikon D3400 is significantly lighter (137g ) than the Canon T7i which may become a big advantage especially on long walking trips.
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 both Canon T7i and Nikon D3400 have the same APS-C sized sensor, their lenses for a similar focal length and aperture will be similar in size and weight.
Unfortunately neither Canon EOS Rebel T7i / EOS 800D / Kiss X9i nor Nikon D3400 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 DSLR Cameras with Weather Sealing
LCD Screen Size and Features
Canon T7i and Nikon D3400's LCD screens has the same diagonal size of 3".
On the other hand, Canon T7i sports a Fully Articulated screen
which you can change the angle and position of the screen almost freely, making it possible to shoot from waist or over the head levels, and especially very useful for shooting selfies and video. Nikon D3400's LCD screen is a fixed type which provides almost no flexibility in shooting positions compared to T7i.