Below you can see the front view size comparison of Sony A7 III and Canon R. Sony A7 III is clearly the smaller of the two cameras. Its body is 9mm narrower, 2mm shorter and 10mm thinner than Canon R.
Sony A7 III vs Canon R - Front View
Sony A7 III vs Canon R - 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