Spot size is measured in which unit?

• A. mm
• B. Centimeters
• C. Micrometers
• D. Inches

Answer: (A)

Spot size in laser hair removal is the diameter of the laser beam as it hits the skin. The standard unit for this measurement is millimeters because the typical spots are only a few millimeters across, like 2–10 mm. Using millimeters lets you gauge how much skin area a single pulse will cover and how energy density changes with different spot sizes. A larger spot covers more area but spreads the energy over a bigger surface, lowering fluence; a smaller spot concentrates energy, increasing fluence and treatment precision. Centimeters would be too large, micrometers are far too small for beam diameter on skin, and inches would be impractical for precise control.