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 Fujifilm X-A3 and Fujifilm X-T100 side-by-side from the front, back and top in their relative dimensions. Fujifilm X-A3 has external dimensions of 117 x 67 x 40 mm (4.61 x 2.64 x 1.57″) and weighs 339 g (0.75 lb / 11.96 oz) (including batteries). Fujifilm X-T100 has external dimensions of 121 x 83 x 47 mm (4.76 x 3.27 x 1.85″) and weighs 448 g (0.99 lb / 15.80 oz) (including batteries).
Below you can see the front view size comparison of Fujifilm X-A3 and Fujifilm X-T100. Fujifilm X-A3 is clearly the smaller of the two cameras. Its body is 4mm narrower, 16mm shorter and 7mm thinner than Fujifilm X-T100.
Here is the back view size comparison of Fujifilm X-A3 and Fujifilm X-T100.
Now lets look at the top view comparison of Fujifilm X-A3 and Fujifilm X-T100.
Weight is another important factor especially when deciding on a camera that you want to carry with you all day.
Fujifilm X-A3 is significantly lighter (109g ) than the Fujifilm X-T100 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 Fujifilm X-A3 and Fujifilm X-T100 have the same Fujifilm X lens mount and APS-C sized sensors, lenses will not be a differentiator on total size of the system.
Unfortunately neither Fujifilm X-A3 nor Fujifilm X-T100 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
Fujifilm X-A3 and Fujifilm X-T100'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.