This is my avatar, the one on the left is about 180 cm or 6ft tall, like I am in RL.
Height – 28 (about 6ft)
Head size – 79
Arm length – 70
Hand size – 50
Torso length – 55
Leg length – 61
Foot size – 0
The one in the middle is the standard avatar called ‘Professional Female’, not one of the tallest but already 2 meters tall.
Finally the one on the right is an avatar that has been maxed out, the tallest female avatar I could create.
As you can see she is about 2.5 meters tall.
On the far right you see the only real scale available in SL; the basic prim, 0.5, 0.5 by 0.5 meters.
I’ve found that this is the only way to make sure your avatar has a realistic size, build a sim that is your size and stand next to it.
I have build a sim in semi-real scale; The 1920s Berlin Project
You can imagine what it would look like if I made doors that the extreme avatars could fit trough.
You can imagine what happens if someone someone of extreme size would sit on a chair made for realistic avatars.
You can find pictures of my adventures visiting sims build for giants here;