Length in appearance

Is the length in appearance ment to be in inches.?

I get a bit confused sometimes. because doors seems to be so high compared to my length.

Height (and all other parameters in appearance) is on an arbitrary scale from 1-100. Other parameters, like leg, torso & hip length can also affect your avatar height. Without using add-ons like 'tiny' poses and animations that lift you off the ground, height goes from a (VERY APPROXIMATE) minimum of 1.2m to a maximum of 2.4m (4-8 feet).

Note also that height measuring gadgets actually measure the avatars bounding box, which only goes up to about eye level. My avatar is about 6 feet tall when measured by a height detector. If I measure it accurately, by checking the distance between prims at my feet and head height, I'm nearly 6 inches taller! In SL, this is considered at the low end of average height.

A lot of builds have very large rooms with high ceilings because of the common standard of using the third person camera view. The camera hovers a bit behind and above your av, so RL-sized rooms are hard to navigate as the camera keeps moving into walls. I've seen houses where the builder has tried to keep the doors in proportion to the ceiling height, ending up with doors 6m or so high, and even the tallest avatars barely reaching the doorknob

The cynical might note that a side effect of this is that you need much more land than you expect if you want to build a house! iRL, a 10m x 10m room is pretty spacious, in SL, it feels like you can barely turn around without bumping into a wall. And we wonder why LL encourages such tall avs...