Size and weight are big decision factors when you are trying to find the ideal camera for your needs.
In this section, we are going to illustrate the Pentax K110D and Pentax K100D side-by-side from the front, back and top in their relative dimensions. Pentax K110D has external dimensions of 129 x 93 x 70 mm (5.08 x 3.66 x 2.76″) and weighs 585 g (1.29 lb / 20.64 oz) (including batteries). Pentax K100D has external dimensions of 129 x 93 x 70 mm (5.08 x 3.66 x 2.76″) and weighs 660 g (1.46 lb / 23.28 oz) (including batteries).
Below you can see the front-view size comparison of the Pentax K110D and the Pentax K100D. In this case, we can see that Pentax K110D and Pentax K100D have the exact same height, width and thickness.
Here is the back view size comparison of the Pentax K110D and Pentax K100D.
Weight is another important factor, especially when deciding on a camera that you want to carry with you all day.
Pentax K110D is 75g lighter than the Pentax K100D but we don't think this will make a significant difference.
Also keep in mind that body weight is not the only deciding factor when comparing two interchangeable camera bodies, you also have to take into account the lenses that you will be using with these bodies. Since both Pentax K110D and Pentax K100D have the same Pentax KAF lens mount and APS-C sized sensors, lenses will not be a differentiator on total size of the system.
Weather Sealing
Unfortunately neither the Pentax K110D nor Pentax K100D provides any type of weather sealing in their bodies, so you have to give extra care especially when you are shooting outdoors. If weather sealing is a must-have feature for you, check these sections: Top DSLR Cameras with Weather Sealing
LCD Screen Size and Features
Pentax K110D and Pentax K100D's LCD screens have the same diagonal size of 2.50 inches.
Unfortunately, both cameras has fixed screens so they don't tilt or flip in directions.