Below you can see the front view size comparison of Panasonic S1R and Nikon D850. Nikon D850 is 3mm narrower and 18mm thinner than Panasonic S1R but it is also 14mm taller.
Panasonic S1R vs Nikon D850 - Front View
Panasonic S1R vs Nikon D850 - 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