Below you can see the front view size comparison of Nikon D610 and Nikon D80. Nikon D80 is clearly the smaller of the two cameras. Its body is 9mm narrower, 10mm shorter and 5mm thinner than Nikon D610.
Nikon D610 vs Nikon D80 - Front View
Nikon D610 vs Nikon D80 - 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