Parkland formula
The burn percentage in adults can be estimated by applying the Wallace rule of nines ( see total body surface area ) : 9% for each arm , 18% for each leg , 18% for the front of the torso , 18% for the back of the torso , and 9% for the head and 1% for the perineum . 
<triplet> torso <subj> perineum <obj> has part <triplet> perineum <subj> torso <obj> part of