Compression Sock Levels, mmHg and Fit
The mmHg number on compression socks is the squeeze in millimeters of mercury; 15-20 is lighter and 20-30 firmer, and a good pair feels tight at the ankle.
By Adolph GreenContributing writer.
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The short answer
Compression socks gently squeeze the leg to help move blood up the legs. The number on the package, such as 15-20 mmHg, tells you how hard they squeeze. Lower numbers are lighter. MedlinePlus advises asking your health care provider which kind is right for you.
What does mmHg mean on compression socks
mmHg stands for millimeters of mercury, the same unit used for blood pressure. On compression wear it gives the pressure the sock puts on the leg. Labels give it as a range, such as 20-30. Pressure also changes along the leg: MedlinePlus explains that you feel the most pressure around the ankle and less higher up the leg. That is why they are also called gradient stockings.
15-20 vs 20-30 mmHg
A 2026 review in the journal Phlebology looked at which pressures help in which conditions:
| Condition | Pressure the review found useful |
|---|---|
| Tired, aching legs or spider veins | 10 to 21 mmHg |
| Uncomplicated varicose veins | 18 to 32 mmHg |
| Preventing leg swelling from vein disease | 15 to 21 mmHg |
| Lymphedema, maintenance phase | 23 to 32 mmHg |
| Healing active leg ulcers | 40 to 50 mmHg |
In that light, 15-20 mmHg sits in the low range the review links to mild symptoms and swelling prevention. 20-30 mmHg reaches into the range it links to varicose veins. The authors note that people wear higher pressures less consistently, and that national standards for compression classes differ, so a "class 1" label in one country may not match another. Read the mmHg number, not just the class.
If you have a medical condition, ask your provider for a prescription that names the pressure and length. MedlinePlus suggests checking whether your insurance pays for compression stockings and having your legs measured at a medical equipment store.
How should compression socks fit
MedlinePlus gives practical fit and wear advice:
- Tight, not painful: the stockings should feel tight around your legs, tightest at the ankle.
- Knee-high length: the top should sit 2 fingers below the bend of the knee.
- No wrinkles: smooth them out and do not let them bunch up.
- Put them on early: first thing in the morning, when legs are least swollen.
- Wash daily: mild soap and water, air dry. Two pairs let you wear one while the other dries.
- Replace them: every 3 to 6 months so they keep their squeeze.
If they are hard to pull on, lotion that has fully dried, a little cornstarch, rubber gloves or a stocking donner can help. If a pair feels too uncomfortable, contact your provider rather than simply stopping.
Lengths
Compression wear comes in knee-high, thigh-high and other lengths, according to MedlinePlus. For shoe-size based sock charts, see our guide to sock sizes.
How we count
Pressure ranges come from Mosti, Benigni and Caggiati, "What is the recommended compression pressure for different clinical indications?", Phlebology, 2026. A read-only query of our listing data on October 26, 2026 found 115 compression socks in the sports and outdoors department on Wiki Shopping, including 23 knee-high and 13 calf styles. The counts change as listings are added or removed.