Size and weight is a big decision factor when you are trying to find the ideal camera for your needs.
In this section, We are going to illustrate Ricoh G900 and Pentax K-3 side-by-side from the front, back and top in their relative dimensions. Ricoh G900 has external dimensions of 118 x 66 x 33 mm (4.65 x 2.6 x 1.3″) and weighs 247 g (0.54 lb / 8.71 oz) (including batteries). Pentax K-3 has external dimensions of 131 x 100 x 77 mm (5.16 x 3.94 x 3.03″) and weighs 800 g (1.76 lb / 28.22 oz) (including batteries).
Below you can see the front view size comparison of Ricoh G900 and Pentax K-3. Ricoh G900 is clearly the smaller of the two cameras. Its body is 13mm narrower, 34mm shorter and 44mm thinner than Pentax K-3. As you can tell, actually this is not a fair size comparison since Ricoh G900 has a built-in lens but Pentax K-3 doesn't. Once you put a lens on K-3, its thickness will increase significantly.
Here is the back view size comparison of Ricoh G900 and Pentax K-3.
Now lets look at the top view comparison of Ricoh G900 and Pentax K-3.
Weight is another important factor especially when deciding on a camera that you want to carry with you all day.
Ricoh G900 is significantly lighter (553g ) than the Pentax K-3 which may become a big advantage especially on long walking trips.
Again, this comparison may not be very useful in real life as we are comparing the weight of a camera with a built-in lens to the body-only weight of an interchangeable lens camera. Once you put a lens on K-3, the total kit will weigh much higher.
LCD Screen Size and Features
Pentax K-3's 3.20" LCD screen is slightly larger than Ricoh G900's 3" screen.
Unfortunately, both cameras has fixed screens so they don't tilt or flip in directions.