Below you can see the front view size comparison of Canon 77D and Canon 80D. Canon 77D is clearly the smaller of the two cameras. Its body is 8mm narrower, 5mm shorter and 3mm thinner than Canon 80D.
Canon 77D vs Canon 80D - Front View
Canon 77D vs Canon 80D - 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