Fingertip units (FTU) can be used to determine the appropriateness of topical drug dosing. An FTU is a very simple way to determine the appropriate dosage of a topical medication. One FTU is the amount of topical medication squeezed from a standard packaged tube (5mm caliber) to one fingertip of an adult, and one fingertip is the length from the tip of the index finger to the first knuckle. It helps physicians and patients to better control the amount of topical medication applied to different parts of the body: 0.5 fingertip units on one side of the hand, 2.5 fingertip units on the face + neck, 7 fingertip units on the front or back of the trunk, 3 fingertip units on one upper extremity, 6 fingertip units on one lower extremity, and 2 fingertip units on one foot, for example. If the disease is in a small child at home, measure the FTU amount on the adult index finger first. One FTU used on a child’s skin is equivalent to two times the size of the palm surface of an adult hand (including the fingers). In other words, measure the area of skin lesions on the child’s skin with an adult hand first, and then convert the adult FTU to the amount of topical medication for the child. This is a simple and practical way to calculate the amount of topical medication for dermatological diseases to achieve the desired efficacy and to reduce its side effects.