Below you can see the front view size comparison of Pentax K-3 and Pentax K-70. Pentax K-70 is clearly the smaller of the two cameras. Its body is 5mm narrower, 7mm shorter and 3mm thinner than Pentax K-3.
Pentax K-3 vs Pentax K-70 - Front View
Pentax K-3 vs Pentax K-70 - 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