How to Choose Compression Socks for Flying: Size, Length and mmHg
Most complaints about compression socks on flights come down to one thing: the wrong size. Socks that slide down and bunch, socks that dig in behind the knee, socks you can't get on in a cramped seat. All of those are fit problems you can avoid before you order. Here's how.
Step 1: Measure your calf
Shoe size tells a sock chart how long to make the foot. It says nothing about your calf, and the calf is where compression socks fit or don't.
- Use a soft tape measure. Wrap it around the widest part of your calf, usually about halfway between your knee and your ankle.
- Keep the tape snug, not tight. Write the number down in inches.
- If one leg is bigger, use the bigger number.
- Owners on travel forums suggest measuring in the morning, before a day on your feet changes the number.
Some charts also ask for your ankle, measured at the narrowest point just above the ankle bone.
Step 2: Read the size chart, not just the size
Now compare your calf number and your shoe size with the brand's chart. There are three kinds of chart, and they're not equal:
- Calf measurement plus shoe size. The best kind. Each size lists a calf range and the shoe sizes it fits. Comrad, Physix Gear and SB SOX print charts like this.
- Shoe size only. Common on two-size socks. You're guessing about the calf. Sockwell's Circulator listing and CHARMKING's listing text work this way.
- A chart in a picture. Some listings point you to a size-chart image instead of printing the numbers. Open it and read it before you order.
Two rules that brands print and owners repeat:
- If you're between sizes, size up. Comrad says so on its listing. A slightly roomy sock is easier to live with than one that cuts in.
- Look for a wide-calf version at your shoe size. On most charts, a bigger calf means a bigger size, which also means a longer foot. A wide-calf fit solves that. The Comrad Knee High comes in Medium Wide Calf and Large Wide Calf for exactly this reason.
If your calf measures over 20 inches, check the top of the chart. SB SOX runs to 24 inches; several brands stop at 19 or 20.
Step 3: Understand the mmHg number
Compression socks list their firmness as a range in mmHg, a unit of pressure. The two ranges you'll see most often on travel socks:
- 15-20 mmHg. Makers label this "mild" or "moderate." It's the level most socks marketed for travel and everyday wear print.
- 20-30 mmHg. Makers label this "moderate" or "firm." It's a tighter sock, and owners say it takes more effort to pull on.
Most socks also say "graduated," which means the pressure is strongest at the ankle and eases as it goes up the leg.
What those numbers do for your legs, and which one you should wear, are medical questions. This site doesn't give medical advice. If you're not sure which level is right for you, ask a doctor or pharmacist first. Our job here is to help you read the label.
One practical tip from owners on travel forums: wear a new pair around the house for a few days before the flight, so you find out whether the size is right while you can still exchange them.
Step 4: Pick a length
- Knee high. The standard length for travel. The top band sits just below the knee. If the sock is too long for your leg, the band ends up behind the knee, which is the "digging in" complaint. Shorter travelers on forums say some brands run long, so check whether the listing mentions length.
- Crew or ankle. These stop below the calf and cover less of the leg.
- Sleeves. A calf tube with no foot, sized by calf measurement.
Never fold a knee-high's top band down to shorten it. Brands say to wear the sock at its full length, with the band flat in one layer.
Step 5: Choose a fabric you can sit in for hours
Owners' most common comfort complaint after fit is heat. Listings describe fabric in a few ways:
- Nylon and spandex. The most common blend. Thin and quick to dry. Look for the words "breathable" or "moisture-wicking" on the listing.
- Merino wool or bamboo blends. Brands such as Sockwell say these manage moisture and regulate temperature. Some forum owners say they feel cooler than nylon; others avoid wool. Personal taste.
- Cushioning. Some socks list a cushioned sole or reinforced heel and toe; others are thin. It's about what you like under your foot.
Check the care label too. Machine-washable socks are easier on a trip.
Step 6: Put them on right
Put them on before you leave for the airport, not in your seat. Turn the sock inside out down to the heel, slip your foot in, then roll the leg up and smooth out any wrinkles. Pack a spare pair for the return flight.
The bottom line: measure your calf, then pick a knee-high
Measure your calf, pick a chart that lists calf sizes, size up if you're between, and buy a knee-high in a fabric you'll be comfortable in for hours. For five socks compared on exactly those points, see our best compression socks for flying.