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 Nikon L31 and Pentax K-5 side-by-side from the front, back and top in their relative dimensions. Nikon L31 has external dimensions of 96 x 59 x 29 mm (3.78 x 2.32 x 1.14″) and weighs 160 g (0.35 lb / 5.64 oz) (including batteries). Pentax K-5 has external dimensions of 131 x 97 x 73 mm (5.16 x 3.82 x 2.87″) and weighs 740 g (1.63 lb / 26.10 oz) (including batteries).
Below you can see the front view size comparison of Nikon L31 and Pentax K-5. Nikon L31 is clearly the smaller of the two cameras. Its body is 35mm narrower, 38mm shorter and 44mm thinner than Pentax K-5. As you can tell, actually this is not a fair size comparison since Nikon L31 has a built-in lens but Pentax K-5 doesn't. Once you put a lens on K-5, its thickness will increase significantly.
Here is the back view size comparison of Nikon L31 and Pentax K-5.
Now lets look at the top view comparison of Nikon L31 and Pentax K-5.
Weight is another important factor especially when deciding on a camera that you want to carry with you all day.
Nikon L31 is significantly lighter (580g ) than the Pentax K-5 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-5, the total kit will weigh much higher.
Thanks to the weather sealed body of K-5, you can use this camera with more confidence under conditions where there is risk of exposure to water and dust compared to L31.
LCD Screen Size and Features
Pentax K-5's 3 LCD screen is slightly larger than Nikon L31's 2.7" screen.
Unfortunately, both cameras has fixed screens so they don't tilt or flip in directions.