Below you can see the front view size comparison of Canon 77D and Panasonic GX8. Panasonic GX8 is 22mm shorter and 13mm thinner than Canon 77D but it is also 2mm wider.
Canon 77D vs Panasonic GX8 - Front View
Canon 77D vs Panasonic GX8 - Top View
The chart below depicts how two cameras compare with average dimensions of the cameras in their class.
Camera Size Comparison
Select Two Cameras for Size Comparison