Botox units are a measure of potency, not volume, and the right dose varies by treatment area, muscle strength, and patient goals. Upper face zones like the forehead, frown lines, and crow's feet typically fall in the 10–30-unit range per area, while the masseter requires 15–50 units per side and underarm hyperhidrosis is treated with around 50 units per axilla per FDA prescribing information. No unit count is universal: in-person assessment by a qualified injector is the only reliable way to determine the correct dosage for each patient.