What Does mmHg Mean in Compression Socks?

mmHg (millimetres of mercury) is the unit that shows how much pressure a compression sock applies, the same unit used for blood pressure. It helps tired, swollen or aching legs by supporting circulation. The catch: the right level depends on your needs and fit, not the highest number. Check with a clinician first if you have circulation problems. 

What Does mmHg Mean in Compression Socks?

You pull a pair off the shelf and there it is on the label: 15-20 mmHg. Not a size, not a colour, just two numbers and a unit most of us last saw at the doctor's. So what is it actually telling you?

What mmHg Means (and why it's the same as blood pressure)

mmHg is a standard pressure measurement. Your blood pressure reading uses it too. On a compression garment, it simply describes the amount of squeeze the fabric puts on your leg.

The bigger the number, the firmer the pressure. That's the whole idea behind the label.

Why mmHg in Compression Socks Is a Range, Not One Number

A rating like 15-20 mmHg isn't a "pick a number in between" scale. It reflects graduated compression: the fabric presses hardest at the ankle (the higher figure) and gradually relaxes toward the top (the lower figure).

Why build them that way? Because gravity pulls blood and fluid down into your lower legs when you sit or stand for long stretches. A firm ankle and a gentler thigh gently encourage that fluid back up toward the heart. If you want the physiology, our guide covers it here: What Do Compression Stockings Do?

That upward assist is also why the fit at the top matters so much, which we'll come to with thigh-highs.

Compression Levels by mmHg

Here's how the common levels line up and who tends to use them. Always confirm the right level with your GP or specialist.

Light support (8-15 mmHg)

Everyday, over-the-counter comfort. Handy for long flights and travel or a day on your feet, with no medical condition involved.

Class 1, Mild (15-20 mmHg)

The usual starting point for medical-grade daily wear. Good for early varicose veins, heavy, tired legs, mild swelling, pregnancy support and long hours sitting or standing. Browse the 15-20 mmHg range.

Class 2, Moderate (20-30 mmHg)

Firmer everyday support for persistent swelling and oedema, more noticeable varicose veins, and clinician-guided recovery. See the 20-30 mmHg range.

Class 3, Firm (30-40 mmHg)

Stronger, prescription-style pressure for significant venous insufficiency, lymphoedema or advanced conditions. Use only under medical supervision. See the 30-40 mmHg range.

You may also spot a second set of numbers on some brands (18-23, 23-32, 34-46). That's a different European classification for the same idea; your fitter can translate it.

Choosing the Right mmHg Level for You

Two rules make this simple.

Match the level to your symptoms, not to "stronger is safer." Wearing too firm a level can be uncomfortable and, in some people, counter-productive. If you've never worn compression, most Australian clinicians suggest starting around 15-20 mmHg.

Match the length to where the problem sits. If swelling or veins reach above the knee, a thigh-high or pantyhose covers the area a knee-high can't. Our comparison walks through it: Knee-High or Thigh-High Compression Stockings?

Then get the size right. mmHg only works as intended when the garment fits, too loose and it slips, too tight and it digs in. Measure against our Compression Stockings Size Chart before ordering.

mmHg and Fit: Thigh-Highs That Actually Stay Up

Here's the part people miss. The right mmHg means little if the stocking slides down by lunchtime, the graduated pressure ends up in the wrong place. That's why every thigh-high in our range uses a silicone top band (topband) that grips the skin and holds the garment where it belongs.

If you want thigh-high support that stays put, these are worth a look:

• Sigvaris Cotton Thigh High with Waist Band, silicone band plus an optional waist attachment for the most secure hold.
• JOBST UltraSheer Thigh High, sheer everyday style with a grip top band.
• SIGVARIS Soft Opaque Thigh High, opaque microfibre with a comfortable silicone border.
• JUZO Soft Thigh High, soft, durable knit with a secure top band.
• Bauerfeind VenoTrain Soft Thigh High, breathable Class 1-2 option with a broad grip band.
• JOBST For Men Thigh High, discreet men's design in black or khaki with a stay-up band.

Prefer to see everything in one place? Browse the full thigh-high compression stockings collection. If you tend to check your toes or wear open shoes, open-toe styles are available too.

Conclusion

You now know that mmHg is simply the pressure rating on compression socks, shown as a range because the squeeze is firmest at the ankle. The best level is the one that matches your symptoms and fits well, not the highest number on the shelf. Confirm your level with your GP if you have any health concerns, measure carefully, then choose a length and stay-up fit that suits your day.

Frequently Asked Questions

Is mmHg the same as blood pressure?

It's the same unit of pressure, yes, but a different measurement. On socks, it describes the squeeze on your leg, not the pressure inside your arteries.

Is a higher mmHg better?

No. Higher just means firmer. Too much pressure can be uncomfortable or unsuitable, especially with circulation issues. Match the level to your needs, not to the biggest number.

Why does the label show two numbers like 20-30?

Because compression is graduated, the higher figure is the firm ankle pressure; the lower figure is the gentler pressure near the top of the garment.

Do I need a prescription to buy compression socks?

Light and Class 1 (up to 15-20 mmHg) are widely available without one. Firmer 30-40 mmHg is best used under medical guidance, and a clinician's advice is sensible at any level if you have health concerns.