The Rule of Nines for burns is the way medical professionals calculate the TBSA (total body surface area) that has been burned. It is important to calculate the TBSA for two reasons:
- It is part of the burn center referral criteria to determine if the patient needs to be admitted to a burn unit.
- It is used to determine how much fluids the patient needs.
Why is the Rule of Nines used to calculate the TBSA?
The Rule of Nines gives medical professionals a way to quickly calculate how much of the body has sustained burn injury. This standard also ensures a consistent measure of TBSA. The Rule of Nines should achieve the same result in New York as it does in Texas, California, or anywhere in between. If a patient is transferred from one medical facility to another, consistency is vital.
How does the Rule of Nines work?
You can learn more about the Rule of Nines and other methods for calculating TBSA in our TBSA infographic. Here is quick rundown:
Rule of Nines for burns on adults:
The entire surface of the human body is divided into 11 areas, with each given a value of 9%. This adds up to 99% of the surface of the body, with the groin being the final 1%. These 11 areas are:
- The head: front of head = 4.5%; back of head = 4.5%
- Right arm: front of arm = 4.5%; back of arm = 4.5%
- Left arm: front of arm = 4.5%; back of arm = 4.5%
- Right leg: front of leg = 9%
- Right leg: back of leg = 9%
- Left leg: front of leg = 9%
- Left leg: back of leg = 9%
- Torso: top half = 9%
- Torso: bottom half = 9%
- Back: top half = 9%
- Back: bottom half = 9%
Adults and children have different body proportions, so the Rule of Nines is different for children. They have proportionally larger heads and shorter legs than adults.
Rule of Nines for burns on children:
The entire surface of the body is divided into 7 areas, with these percentages:
- Head: front and back total = 18%
- Torso: front = 18%
- Torso: back = 18%
- Right arm: front and back total = 9%
- Left arm: front and back total = 9%
- Right leg: front and back total = 14%
- Left leg: front and back total = 14%
Note that for both adults and children, some areas are given a greater proportion than their actual surface area would warrant. This is because injury to these areas is more dangerous than injuries to other areas. This includes the face and neck, groin and buttocks, and joints.
How Medical Professionals Apply the Rule of Nines
Example: A person has burns covering the entire front of the left arm. The TBSA is 4.5%.
Example: A person has burns covering the top half of the back of the left arm and the top of the back. The TBSA is 2.25% for the burned portion of the arm and 9% for the burned portion of the back, for a total TBSA of 11.25%.
Example: A person has burns covering the groin, the entire front of the right leg, the top half of the front of the left leg and the top of the back of the right leg. The TBSA is 1% for the groin, 9% for the front of the right leg, 4.5% for the front of the left leg, and 4.5% for the back of the right leg, for a total TBSA of 19%.
The Rule of Nines for burns is not the only method for estimating TBSA. Some medical professionals may use the Lund Browder Method, especially for infants and small children, or the palmar method. Learn about these methods and more about TBSA in our infographic.