Below you can see the front-view size comparison of the Fujifilm X-A5 and Fujifilm X-T100. The Fujifilm X-A5 is clearly the smaller of the two cameras. Its body is 4mm narrower, 15 mm shorter and 7 mm thinner than the Fujifilm X-T100.
The chart below depicts how two cameras compare with average dimensions of the cameras in their class.