How to Memorize the Rule of Nines
With Amboangel's Tap Technique

First, let us clarify some vocabulary. The body part that the average person calls a leg is often called a lower limb in the medical literature. In and of itself, this is not a problem, but the picture gets clouded when the lower limb is defined as consisting of a thigh, a knee, a leg, an ankle, and a foot. Likewise, the body part commonly called an arm is often called an upper limb in the literature and is defined as consisting of a shoulder, an arm, an elbow, a forearm, a wrist, and a hand. On this page, I will use the definitions for arm and leg that I have used since preschool and describe the technique as though I am teaching it to a layperson.

The Rule of Nines for Adults

For an adult of normal, healthy weight, the patient's body surface is divided into 12 areas. Eleven are assigned 9%; the twelfth is assigned 1%. The total is 100% (11 x 9% + 1% = 100%). The assigned areas for an average adult are:

The Tap Technique

Knowing that there are eleven equal areas facilitates a physical technique to memorize the rule of nines: Tap your own body rhythmically on or near each of the large assigned areas to represent 99 percentage points; then tap your belt for the final 1%. (A groin-grab would be more accurate and memorable but is generally considered to be outside of the social norm.) Count each tap aloud.

In other words, tap your right leg twice with your right hand while saying "one-two." Tap your left leg twice with your left hand while saying "three-four." Tap your abdomen and tap your chest while saying "five-six." Tap your back twice while saying "seven-eight." Tap your left arm and then your right arm while saying "nine, ten." Tap your head and say "eleven." Finally tap your belt and say ""one." The sum is 100%. Do this a few until it is remembered. Repeat it a few times in the future so it stays remembered.

The Rule of Nines for Children

The criteria for the rule of nines is somewhat different for children because children have proportionally larger heads and smaller legs. (There is not a clear line separating children from adults.) In some protocols, the head of a child is assigned 12 percentage point, which is 3 more than for the head of an adult; and the legs are assigned 33 percentage points, which is 3 less than for the legs of an adult. One way to remember this is to tap out adult criteria and then add two taps onto the end, tapping the head and legs and saying "three, three" or "thirty-three." In other protocols the bodily proportions of children are considered close enough to those of infants that rule of nines for infants is also applied to children.

The Rule of Nines for Infants

For infants, the legs of are assigned 9 percentage points less than those for the legs of an adult, and the head is assigned 9 percentage points more than those for the head of an adult. The tap technique can be easily modified to accommodate this: Tap your right leg once with your right hand, tap your left leg once with your left hand, tap both legs with both hands at the same time all while counting "one-two-three." Continue with normal tapping the rest of your body with a two-count rhythm except for your head. Your head gets two taps with the count "ten-eleven." Finish with a belt tap and count "one."

The Rule of Eights for Infants

Although not commonly used, the rule of eights was devised for infants weighing less than 22 lbs (10 kg). The assignments for the rule of eights are based on 10 multiples of eight and a 20% remainder like this: 16% for each leg, 32% for the torso, 8% for each arm, and 20% for the head. These assignments can be tapped out twice on each leg for "one, two, three, four," four times on the torso for "five, six, seven, eight," once on each arm for "nine, ten," then once on the head for "twenty." The total is 100% (10 x 8% + 20% = 100%).

The Rule of Fives for Obese Adults

The rule of fives was devised for obese patients weighing more than 176 lbs (80 kg) after questions were raised about the accuracy of the rule of nines for obese patients. The criteria for the rule of fives are based on 20 multiples of five. Each leg is assigned 20%, the torso is assigned 50%, each arm is assigned 5%, and 2% is assigned for the head. Obviously this does not add up to 100%. It equals 102%, which is considered close enough. The rule of fives can be memorized by a two-rhythm tapping as follows: once on each leg for "twenty, twenty," once on the abdomen for "fifty," once on each arm for "five, five," and once on the head for "two."

One more Trick

It is logical to assume that burns that are too large to assess with the palmer method (a patient's palm area = 1% of body area) will require rapid and accurate assessment with one of the burn rules. To develop confidence and proficiency, one can imagine various burns on random persons and visually practice assessing them, Needless to say, this must be done without giving off creepy vibes.