“The Rule of Nines, also known as the Wallace Rule of Nines, is a tool used by trauma and emergency medicine providers to assess the total body surface area (TBSA) involved in burn patients.  Measurement of the initial burn surface area is important in estimating fluid resuscitation requirements since patients with severe burns will have massive fluid losses due to the removal of the skin barrier. Source

The Rule of Nines is also an approach to calculate the percentage of a patient’s total skin surface impacted by PRP. When you tell your story, your estimate of coverage will be more readily believed — by friends and healthcare providers —  if you preface your estimate with the phrase, “Based on the Rule of Nines…yada, yada, yada.” 

• The front and back of the head and neck equal 9% of the body’s surface area.
• The front and back of each arm and hand equal 9% of the body’s surface area.
• The chest equals 9% and the stomach equals 9% of the body’s surface area.
• The upper back equals 9% and the lower back equals 9% of the body’s surface area.
• The front and back of each leg and foot equal 18% of the body’s surface area.
• The groin area equals 1% of the body’s surface area.