CS-01 · Compression Socks
What does mmHg mean on compression socks?
The short answer
It is the pressure the sock is made to apply, measured at the ankle: 15-20 mmHg is everyday support, 20-30 mmHg is firm, and 30-40 mmHg is the level people usually wear on a clinician's advice.
mmHg (millimetres of mercury) is the same unit a blood pressure cuff uses. On a compression sock it tells you how firmly the fabric presses at the ankle, where graduated socks are tightest. It is the one number that separates a compression sock from a snug tube sock.
The three ranges you will see
15-20 mmHg: light to moderate. The range most people pick for long days on their feet, travel, and the heavy, tired feeling in the legs by evening.
20-30 mmHg: firm. A common choice for long flights, twelve-hour standing shifts and people who already know moderate compression suits them.
30-40 mmHg: extra firm. Usually worn because a clinician suggested it. If nobody has, start lower.
Why the number is a range
Pressure depends on how the sock fits your leg. The same sock applies more pressure on a larger ankle and less on a smaller one, which is why makers size by ankle and calf measurement and quote a range rather than one figure.
When to check with a clinician first
If you have diabetes, peripheral arterial disease, numbness in your feet, skin that breaks easily, or swelling in one leg only, talk to your clinician before wearing firm compression. Firm compression is not right for every leg.
Questions people actually ask
Straight answers
Is a higher mmHg always better?
No. Higher only means firmer. The right level is the lightest one that does the job for you, and firmer socks are harder to put on and less comfortable for a full day.
Does a sock with no mmHg rating do anything?
It can feel snug, but without a stated rating you cannot know how firm it is or whether it is graduated. If the number is missing, treat it as an ordinary sock.
Can I sleep in compression socks?
Most people take them off at night because legs are raised and the socks are not needed. Only sleep in them if a clinician told you to.
Updated 2026-09-26. Nothing on this site is medical advice. If you have a condition, talk to your clinician before you buy.