Below you can see the front view size comparison of Sony RX10 IV and Nikon 1 J5. Nikon 1 J5 is clearly the smaller of the two cameras. Its body is 35mm narrower, 34mm shorter and 113mm thinner than Sony RX10 IV.
Sony RX10 IV vs Nikon 1 J5 - Front View
Sony RX10 IV vs Nikon 1 J5 - 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