Below you can see the front-view size comparison of the Olympus E-M1 and Olympus E-M5 II. The Olympus E-M5 II is clearly the smaller of the two cameras. Its body is 6 mm narrower, 9 mm shorter and 18 mm thinner than the Olympus E-M1.
The chart below depicts how two cameras compare with average dimensions of the cameras in their class.