Below you can see the front-view size comparison of the Fujifilm X-T3 and Olympus E-M5. The Olympus E-M5 is clearly the smaller of the two cameras. Its body is 11 mm narrower, 4 mm shorter and 16 mm thinner than the Fujifilm X-T3.
The chart below depicts how two cameras compare with average dimensions of the cameras in their class.