In the acute assessment and management of burn injuries, various methods have been described to estimate the total body surface area (TBSA), which is used to guide clinical decision-making including volume requirements for fluid resuscitation and the potential for patient transfer to specialist burns referral centres. Existing literature have highlighted that TBSA assessments are often inaccurate and overestimations, largely due to human error. This has potentially significant consequences of over-resuscitation, especially in obese patients, which may lead to capillary damage and burn oedema. The Rule of Nines is perhaps the most widely recognised and applied technique by non-specialist burns care providers, including emergency physicians and paramedics. This method involves assigning percentages of TBSA in easily memorable multiples of nine to different body regions. The Lund Browder Chart was developed earlier at Harvard Medical School in 1944 to improve the accuracy of calculation of body surface area in burns. The chart provides age-adjusted body proportions and is accepted as the most accurate graphical record of burn size. The palmar method involves using the patient’s palm as a reference point for estimating TBSA. In its simplest form, the palm is considered 1% of the TBSA, however more recent data has supported using the palmar surface with digits as 0.8% and the palm without digits as 0.5% for adult patients. This presentation will describe and compare the predominantly used methods of TBSA estimation, with attention given to their benefits, limitations and the most appropriate clinical settings for their application.