Mastering Burn Formulas

There is a good chance you’ll see a burn question on the NREMT exam.  Here are a few tips for mastering the burn knowledge and formulas you may need.

Burns are classified by depth: superficial, partial-thickness and full-thickness (see table). The image is a partial thickness burn. Note the blisters, wet appearance and missing layer of epidermis characteristic of the partial thickness burn. This burn tricks some people because they see “charring” and mistakenly classify it as a full-thickness burn.

The Rule of 9s

The rule of 9s is a relatively simple method of remembering body surface area (BSA) for burns. Remember that it is an approximation and you shouldn’t be doing math when you should be resuscitating your patient. Where we mess up most in exam questions is when we are given partial areas. Remember to pay attention to descriptive terms such as anterior/posterior and partial areas. The anterior torso is 18%. You may be given a question where the anterior chest or abdomen are burned. These are each worth 9% BSA each. This is an important difference from 18% for the full anterior torso. The leg is 18% but the anterior leg is 9%. If you get a question which states half of the right arm is burned, the BSA is 4.5%. These small details are the difference between getting an exam question right and wrong.

The Parkland Burn Formula

The Parkland Burn Formula (4 x patient’s weight in kg x BSA burned) is a two-part process with a lot of math involved. This leaves room for errors on two fronts for our advanced students and providers. If you don’t get the BSA correct, you won’t get the formula correct. If you get the formula or calculation wrong, you won’t determine the correct amount of fluid. Remember that half the volume is delivered in the first eight hours. The remainder is delivered over the next 16 hours.

A chart with BSA percentages can be found at