I was never quite in agreement that the Health Percent in Body Part Data was only related to the amount of health that a particular body part has. It just didn't make sense or play that way in game.

First, I had the thought that the Health Percentage related to the damage a body part took before it was dismembered or exploded, but those only occur upon death.

Then I did a little testing under the assumption that the Health Percent actually relates to the amount of damage a body part can take before it becomes crippled. First I tested it on a Brahmin giving the left head a Health Percent of 5 and the right head 95, everything else being equal, and it bore out my hypothesis. Everytime I shot the left head it became crippled with only 1 shot while the right head took 3-4 shots before becoming crippled. The health meter was reduced by the same amount whichever head I shot (barring a critical hit). I tried this test out on a few other creatures and NPC's and all had similar results.

So the Health Percent in Body Part Data is the % of total health at which a body part becomes crippled by damage.

Also, for those who ask the question as I did about the player torso having 255% Health Percent or the legs 150%, there must also be a threshold that will result in that body part being crippled which is well below the total amount of health. That way if a body part has a Health Percent over 99, the damage reaches the Cripple Threshold for that body part before enough damage is done to kill the creature/NPC.

Hoping someone in the know could run a few tests of their own, figure out the correct formula, and change the Wiki page to reflect this info.

Thanx - Mal

Edit: Clarifying Point