To measure compression socks, wrap a soft tape around the widest part of your calf soon after waking, then match it and your shoe size to the size chart.
Most compression socks that come back to us weren't faulty. Someone picked a size from their shoe size, or measured their calf at seven in the evening after a long shift, and the sock arrived made for a different leg. One sock slides down to the ankle by lunchtime. Another digs a red ring under the knee. In both cases, the buyer decides compression socks "don't work".
Getting the size right takes a soft tape measure and about five minutes. For a knee-high compression sock, it mostly comes down to one number that hardly anyone has ever taken: the distance around the widest part of the calf, measured before the day's swelling sets in.
This guide covers the whole process. It explains what to measure, when to measure, how to read a size chart, what to do if your legs differ, and who should get measured by a GP or pharmacist instead of doing it at home. By the end, you'll have two numbers written down and know which size to order, whether the socks are for a long-haul flight, a twelve-hour ward shift, or swelling in pregnancy.
Why Does the Right Size Matter for Compression Socks?
A compression sock only delivers its stated pressure on a leg that sits inside its size range. The mmHg figure on the label (15 to 20 mmHg, for example) describes the squeeze on a calf of the intended circumference. On a wider calf, the pressure climbs. On a narrower one, it drops away, and the graduated effect goes with it. "Graduated" means firmest at the ankle and easing off towards the knee.
Ordering compression socks by shoe size is like buying a belt by your shoe size. Your feet and your waist are loosely related, and so are your feet and your calves.
Two people in a UK size 6 can have very different calves:
One cycles to work every day, the other has spent twenty years behind a reception desk. The sock has to fit the calf, because that's where the work happens.
The wrong size fails in predictable ways. Too small, and the cuff bites, toes tingle, and deep marks stay on the skin long after the sock comes off. Too big, and the fabric wrinkles at the ankle and the sock creeps down your shin while doing very little.
This page is about getting the numbers right before you order. How a sock should feel once it's on is a separate question, and our guide to how tight compression socks should be covers the sensations to expect and the warning signs to act on.
What do you need to measure for compression socks?
You need a flexible fabric tape measure, the kind used for sewing, plus something to write on and a firm chair. A metal DIY tape won't wrap around a leg properly, so leave it in the drawer. If you don't own a soft tape, a length of string or ribbon works. Wrap it around your leg, pinch or mark where it meets, then lay it flat against a ruler.
Measure on bare skin. Leggings, tights, and thin trousers all add a little to every reading, and on a size chart with a narrow overlap, that little can push you into the wrong size. Shorts, or trousers rolled well above the knee, are fine.
When Should You Measure Your Legs for Compression Socks?
Measure first thing in the morning, before you've spent much time on your feet. Legs gain fluid through the day as gravity pulls it downwards, so your calf at bedtime is often noticeably bigger than your calf at breakfast. NHS prescribing guidance from Bristol, North Somerset and South Gloucestershire states that where a leg is swollen, measurements should be taken first thing in the morning.
Our rule of thumb:
Measure the leg you wake up with, not the leg you go to bed with. A sock sized to your evening calf will fit comfortably at 8pm. It will also sit loose all morning, which is exactly when it should be stopping the swelling from building up.
If your legs are swollen most of the time, including first thing, don't rely on home measuring. Speak to your GP or pharmacist first. Ongoing swelling has a cause that needs looking at, and our guide to compression socks for oedema explains what's involved.
How to Measure Your Calf and Ankle
For knee-high compression socks, you need your calf circumference and your shoe size. We also recommend taking your ankle measurement while the tape's out.
Here's the order we suggest.
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Sit down properly. Use a firm chair with both feet flat on the floor and your knees bent at roughly a right angle. This relaxes the calf muscle so you're measuring the leg at rest rather than flexed.
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Find the widest part of your calf. For most people, this is about halfway between the ankle and the back of the knee. Slide the tape up and down a few centimetres and take the largest reading. Keep the tape level, flat against the skin and snug without pressing in, then write the number down in centimetres.
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Measure your ankle. Wrap the tape around the narrowest point, just above the bony bump on either side. Our size chart doesn't use this number, but many other charts and NHS fitters do, and it's the easiest way to spot swelling creeping up over the following weeks.
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Note your UK shoe size. This tells you whether the foot section of the sock will fit. A sock with the right calf and the wrong foot length puts the heel pocket in the wrong place.
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Repeat on the other leg. NHS clinical guidance on stocking fitting says to measure both legs separately, and so do we. Plenty of people are a centimetre or two different side to side.
That's the whole job for knee-highs. Thigh-high compression stockings need more measurements, which we cover in the FAQs below.
How Do You Read a Compression Sock Size Chart?
Read your calf measurement first, then check that your shoe size falls in the same row. Every brand uses its own chart, so a Medium elsewhere tells you nothing about a Medium here.
Our knee-high compression socks are sized by calf circumference and shoe size:
|
Size |
UK shoe |
EU shoe |
Calf (cm) |
Calf (approx. inches) |
|
S |
3 to 6 |
36 to 39 |
30 to 37 cm |
11.8 to 14.6 in |
|
M |
6 to 9 |
39 to 43 |
36 to 43 cm |
14.2 to 16.9 in |
The two sizes overlap slightly, and that's on purpose. If you land in the overlap, go up a size. A cuff that's too tight digs in and does less for your legs, not more. Take someone with a 36.5 cm calf and a UK size 6 foot: both sizes technically fit, and the Medium is the better choice.
When calf and shoe size point in different directions, the calf wins. A foot that's slightly short for the sock is a minor comfort issue. A calf that's squeezed beyond the sock's range changes the pressure on the whole lower leg.
Be honest with yourself if your numbers fall outside the chart altogether, for example, a calf under 30 cm or over 43 cm. Our socks won't fit you well, and forcing them on isn't worth it. A pharmacist can talk you through other sizing options.
If you'd like all of this in one place to keep by the tape measure, our free fit and sizing ebook covers measuring, reading the chart, and checking the fit when your socks arrive.
What If One Leg Measures Bigger Than the Other?
A small difference between legs is normal, and for a pair of socks you should size to the larger leg. Most people find one calf is a centimetre or so bigger than the other, often on the side they lead with when walking or climbing stairs. As long as both measurements sit in the same row of the chart, order that size.
It gets trickier when the difference pushes each leg into a different size. In hospital, NHS staff fitting stockings are told to order two different sizes when legs measure differently. That isn't possible with a standard pair, so speak to a pharmacist before buying.
Pay attention to new swelling in one leg. If one calf has become swollen recently, especially with throbbing pain, warmth or redness, don't buy compression socks. Get urgent advice from NHS 111 or your GP, because the NHS lists these as signs of a possible deep vein thrombosis (DVT).
How Should Compression Socks Fit Once They're On?
A well-fitted compression sock sits smooth against the skin, with the heel centred in the heel pocket and the cuff about two finger-widths below the crease at the back of your knee. You should feel firm pressure around the ankle that eases as you run your hand up towards the knee. Your toes should stay warm, pink, and easy to wiggle.
Put them on in the morning and smooth out any wrinkles as you go. A fold of fabric over the ankle bone turns into a pressure line after a few hours. If the sock feels long, don't fold or roll the top down. An NHS leaflet from Cambridge University Hospitals warns that a rolled top can act like an elastic band on the leg below it.
Take the socks off if you notice numbness, pins and needles, pain, or toes that turn pale, blue or cold. Those signs point to the wrong size or a reason compression isn't right for you. Socks that slide down or bunch at the ankle are the opposite problem: almost always a size too big, or a pair that has lost its stretch.
Common Mistakes When Measuring For Compression Socks
The most common mistake is pulling the tape tight "to be safe". Squeezing the tape gives a smaller number, which leads to a smaller sock, which is the one that digs in. The tape should touch the skin all the way round without leaving a mark.
Measuring at the wrong height comes a close second. The widest point of the calf sits higher than many people expect, and a reading taken just above the ankle can be 10 cm or more under your true calf size. Slide the tape up and down before you commit to a number.
Then there's timing. Measuring after a day on a hospital ward, a shop floor, or a flight gives you a swollen leg's size, and the sock will be loose on your normal leg. The last mistake is reusing old numbers. A measurement from two years and one marathon training block ago describes someone else's calf.
Is It Safe to Measure Yourself and Buy Compression Socks Without Seeing a GP?
For most healthy adults buying 15 to 20 mmHg knee-high socks for travel, long shifts or tired, achy legs, yes. Measuring at home is safe, and so is buying without a prescription. Some people should see a GP, practice nurse or pharmacist first, because compression puts pressure on everything under the fabric, not just the veins.
Speak to a professional before buying if you have, or think you might have, any of the following:
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Peripheral arterial disease (PAD). This is narrowing of the arteries to the legs. NICE explains that the reduced blood flow in PAD is something which can be worsened by compression therapy. Leg pain when walking that eases with rest is a classic sign, and the NHS page on PAD lists the others.
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Diabetes or neuropathy with reduced feeling in your feet. If you can't feel your feet well, you won't notice a sock that's too tight until damage is done.
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Very swollen legs. An NHS leaflet from Sherwood Forest Hospitals lists very swollen legs, PAD and peripheral neuropathy among the situations where stockings may not be suitable.
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Broken, infected or very fragile skin on the lower legs, including leg ulcers.
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Heart failure, unless your care team has said compression is fine.
Our socks are MHRA-registered and medical grade, but no sock replaces an assessment if any of the above applies to you. Our full guide on who should not wear compression socks goes through each condition in more detail.
How Often Should You Re-measure for Compression Socks?
Re-measure every time you replace your socks, which for daily wear is usually every three to six months. NHS guidance from Bristol advises that, ideally, the leg should be re-measured each time a stocking is replaced. North Cumbria's leg ulcer service says people need new hosiery every 3 to 6 months to keep getting the right support.
Some life changes mean measuring again sooner. Weight gain or loss of around a stone can move your calf by a couple of centimetres. So can a new running or cycling habit. Calf and ankle size can shift from month to month through pregnancy, so check every few weeks if you're wearing compression through the second and third trimesters.
If your socks start feeling looser even though your measurements haven't changed, the fabric is the likely culprit. Heat breaks down the elastic fibres, and the right way to wash compression socks makes a real difference to how long a pair holds its squeeze.
Frequently Asked Questions
Can I just use my shoe size to choose compression socks?
No. Shoe size only tells you whether the foot section will fit, and the pressure that matters is applied around your ankle and calf. Two people with the same shoe size can have calves several centimetres apart, so always measure your calf before ordering.
Should I Measure in Centimetres or Inches?
Use whichever unit the size chart uses, which for most UK charts (ours included) is centimetres. Converting adds a small rounding error that matters near the edge of a size. If your tape only shows inches, multiply by 2.54 to get centimetres.
Do Men and Women Measure for Compression Socks Differently?
No. The method is the same for everyone: widest part of the calf, narrowest part of the ankle, and UK shoe size. Our socks are unisex, so the size comes from your numbers rather than your gender.
Do you Measure for Compression Stockings the Same Way as Socks?
For knee-high compression stockings, yes, because they cover the same part of the leg as knee-high socks. Thigh-high stockings also need the circumference of the widest part of the thigh and a leg length, usually from the floor to the top of the thigh. NHS prescribing guidance notes that below-knee stockings are usually better tolerated than thigh-length ones, which helps people keep wearing them.
How Long Should I Wear Compression Socks Once I've Found the Right Size?
Most people put them on in the morning and wear them through the hours they're upright, typically 8 to 12 hours, then take them off before bed. Follow your GP's or surgical team's advice if you've been given specific instructions. Our guide on how long to wear compression socks explains timing for shifts, travel and recovery.
Your Next Step
You now know what a compression sock size depends on: your calf at its widest, measured in the morning, checked against your shoe size and a specific brand's chart. Measure both legs, size to the bigger one, go up if you fall in the overlap, and re-measure whenever you replace your socks or your body changes. If you have PAD, diabetes with reduced feeling, very swollen legs, or broken skin, speak to your GP or pharmacist before you buy.
The simplest thing to do now is leave a soft tape measure next to the kettle. Tomorrow morning, before you've been on your feet for long, sit down and take your calf measurement and your ankle measurement, both legs. Then compare the numbers with the size guide on our 15 to 20 mmHg graduated knee-high compression socks.
Main Squeeze is MHRA-registered, costs £30 for one pair, £54 for two, and £72 for three, and UK delivery is free on orders over £50. Returns are accepted within 30 days if the socks are unworn and in their original packaging, which is one more reason to measure before you order.
If you'd rather have the full checklist to hand while you measure, download the free fit and sizing ebook.
