Quick answer: compression strength is measured in mmHg (millimeters of mercury). 8-15 mmHg is light, for tired legs and everyday comfort. 15-20 mmHg is medium, the most common choice for travel, long days on your feet and mild swelling. 20-30 mmHg is firm, usually for swelling or vein problems your doctor wants treated with more support. If you're not sure, start light, and ask your doctor before going to 20-30 mmHg.
What does mmHg mean on compression socks?
mmHg is a unit of pressure, the same one used for blood pressure. On a compression sock it tells you how much pressure the sock puts on your leg at the ankle, where it's firmest. Graduated compression socks are tightest at the ankle and ease off gradually up the leg, which helps move blood and fluid back up toward the heart instead of letting it collect in the lower legs.
A range like 15-20 mmHg means the ankle pressure falls somewhere in that range, depending on your exact leg size. That's one reason fit matters: the same sock is firmer on a larger calf and lighter on a smaller one.
Compression levels at a glance
| Level | How it feels | Common uses | Doctor's advice? |
|---|---|---|---|
| 8-15 mmHg (light) | Gentle, like a snug sock | Tired, achy legs; long days sitting or standing; first-time wearers | Not usually needed |
| 15-20 mmHg (medium) | Noticeably supportive | Travel and flights, mild swelling by the end of the day, pregnancy (with your doctor's OK), standing jobs | A good idea if you have a medical condition |
| 20-30 mmHg (firm) | Firm; takes effort to put on | Moderate swelling, varicose veins, vein problems, after some procedures | Recommended |
| 30-40 mmHg and above | Very firm | Severe swelling, lymphedema, specific vein conditions | Prescribed and fitted |
8-15 mmHg: light compression
Light compression is the easiest to put on and to wear all day. It suits people who want their legs to feel less heavy after a long day, who sit for hours at a desk or in the car, or who are trying compression for the first time. If you have diabetes or neuropathy and your doctor is happy for you to try compression, this is usually the level to start with.
15-20 mmHg: medium compression
This is the most popular over-the-counter strength. It's a common pick for flights and long car trips, for jobs where you're on your feet all day, and for mild swelling that shows up by evening. It's firm enough to feel, but most people can put it on themselves and wear it comfortably from morning to bedtime.
20-30 mmHg: firm compression
20-30 mmHg is often called medical-grade. It's typically used for swelling or vein problems (such as varicose veins) that a doctor wants treated with firmer support, or after certain procedures. It takes more effort to pull on, so a sock aid or rubber gloves can help. Because it's firm, it isn't right for everyone. People with circulation problems in the arteries (peripheral artery disease), certain heart conditions, or reduced feeling in their feet should get medical advice first.
How to choose the right compression level
- Start with why you want compression. Tired legs: light. Travel or standing all day: medium. Swelling or vein problems your doctor is treating: firm, as advised.
- Start lower if you're unsure. It's easy to go up a level later. A sock that's too firm to put on or wear won't help.
- Size by your leg, not just your shoe. Measure your ankle and calf in the morning and use our compression socks size chart.
- Check with your doctor before using 20-30 mmHg, or any compression if you have diabetes, neuropathy, artery disease or skin problems on your legs.
Signs your compression is too strong
- Numbness, tingling or pins and needles in your toes
- Toes that look pale, blue or dusky, or feel cold
- Pain that gets worse while wearing them
- Deep marks that don't fade within about 30 minutes of taking them off
If you notice any of these, take the socks off and try a lighter level or a different size. See how long to wear compression socks for wear-time advice.
Our compression socks come in all three levels
Our men's and women's over-the-calf compression socks come in 8-15, 15-20 and 20-30 mmHg, and you can choose a different strength for each pair. That makes it easy to try a lighter pair for everyday and a firmer pair for travel. They're graduated, knit from a breathable nylon and spandex blend, made in Alabama, and ship free. See the full compression collection.
Frequently asked questions
Is 15-20 or 20-30 mmHg better?
Neither is better in general. 15-20 mmHg suits most everyday uses like travel and standing jobs. 20-30 mmHg is for when you need firmer support, usually on a doctor's advice.
What compression level is best for seniors?
Most older adults do well starting at 8-15 or 15-20 mmHg, which are easier to put on and comfortable to wear all day. Go firmer only if your doctor recommends it.
What compression level is best for swelling?
Mild swelling often responds to 15-20 mmHg. For more noticeable swelling, a doctor may suggest 20-30 mmHg. New or one-sided swelling should always be checked by a doctor.
Do I need a prescription for 20-30 mmHg compression socks?
In the US you can buy them without a prescription, but it's still a good idea to ask your doctor, especially if you have diabetes, neuropathy or circulation problems.
What compression level is best for flying?
15-20 mmHg is the most common choice for flights. Put them on before you travel.
This article is general information, not medical advice. Updated September 2026.
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