mmHg stands for millimeters of mercury, which is a unit of pressure measurement. In the context of compression stockings, it indicates the amount of pressure the garment applies to your leg. The higher the mmHg, the stronger the compression. This pressure helps improve blood flow and reduce swelling.
15–20 mmHg = mild compression (for tired, achy legs, mild swelling, minor varicosities during pregnancy)
20–30 mmHg = moderate compression (commonly prescribed for moderate to severe varicose veins, moderate edema, moderate to severe varicosities during pregnancy, or mild lymphedema)
30–40 mmHg = firm compression (for more severe conditions, usually under medical supervision such as severe varicosities, severe edema, lymphatic edema, chronic venous insufficiency)