Below you can see the front-view size comparison of the Olympus TG-870 and Fujifilm X-T1 IR. The Olympus TG-870 is clearly the smaller of the two cameras. Its body is 16mm narrower, 26 mm shorter and 19 mm thinner than the Fujifilm X-T1 IR.
The chart below depicts how two cameras compare with average dimensions of the cameras in their class.