 In resuscitation, knowing a patient's weight is essential for administering the correct dosage of medication or sizing instruments. Unfortunately, scales are often impractical in emergency situations, so other methods must be used. Visual assessment, age, height, and body habitus can all be used to estimate a patient's weight. However, these methods tend to underestimate a patient's weight as they grow older, due to their changing body habitus. More research is needed to develop more accurate methods of estimating a patient's weight during resuscitation.