Below you can see the front view size comparison of Pentax K-1 II and Nikon D5. Pentax K-1 II is clearly the smaller of the two cameras. Its body is 23mm narrower, 49mm shorter and 6mm thinner than Nikon D5.
Pentax K-1 II vs Nikon D5 - Front View
Pentax K-1 II vs Nikon D5 - 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