In order to maximize their use and efficacy, topical drugs should be applied in a way that is precise and consistent. It is important that this process is standardized, since under- or overapplication can lead to inadequate amounts of medication dispensed or unnecessary risk of medication side effects, respectively. Normally, topical medications should be applied to the skin in a thin layer. One gram of cream will cover an area of skin approximately 10 cm × 10 cm, approximately 100 cm², assuming a layer 100 µm in thickness. That same amount in an ointment vehicle will cover an area 5% to 10% larger. For all types of semisolid topicals, the fingertip unit (FTU) is a practical guide for the amount of drug to cover a specific region. One FTU represents the amount of topical drug expressed from a tube with a 5-mm-diameter nozzle that is applied from the distal skin crease to the tip of the index finger. This amount, roughly 0.5 g, is enough to treat twice the area of skin covered by the palmar surface of a hand. In other words, 1 FTU = 0.5 g = 2 hand areas, 2 FTUs = 1 g = 4 hand areas, and so forth. With this estimate, approximately 20 to 30 g of cream or ointment will cover an adult once. It is important to correctly prescribe the amount of medication needed for a full treatment course.