How We Test Our Compression Socks
Comrad tests its compression socks on a Swisslastic MST MK V, a Swiss-made medical stocking tester, before any production order is approved. The tester measures pressure in mmHg at four points from the ankle to below the knee, in every size, and every reading is checked against our spec. If the pressure isn't graduated, or the ankle reading falls outside our tolerance, the sock doesn't ship.
Key takeaways
- Comrad measures compression with a Swisslastic MST MK V medical stocking tester at the ankle (b), lower calf (b1), calf (c) and below the knee (d).
- Every size, including wide-calf sizes, is measured before a production order is approved.
- Comrad's 15–20 mmHg knee-high measured 19.5–20.3 mmHg at the ankle across sizes S to XL on September 19, 2026.
- Pressure below the knee measured 64–71% of the ankle pressure, which is what graduated compression should look like.
- Comrad holds the ankle reading to ±3 mmHg of the labeled range, and pressure must decrease at every point up the leg.
- Pre-production samples are also tested by SGS, an independent lab, for pilling and colorfastness (Grade 4.5 of 5 in 2026).
Why we measure, not just label
Compression is measured in millimeters of mercury (mmHg), the same unit used for blood pressure. A sock labeled "15–20 mmHg" should press about 15 to 20 mmHg on your ankle and less as it moves up your leg. That decreasing pressure is called graduated compression, and it's the whole point of a compression sock.
The problem: a label is just ink. Knitting machines drift, yarn lots change, and a sock that is a few centimeters too long puts its pressure in the wrong place on your leg. The only way to know what a sock actually does is to put it on a calibrated leg form and measure it.
So that's what we do, and on this page we show you the numbers.
Graduated compression, in one line
Firmest at the ankle, gradually lighter toward the knee. Here is a real Comrad 15–20 mmHg knee-high (size M) measured on Sept. 19, 2026:
The Swisslastic MST MK V medical stocking tester
The Medical Stocking Tester (MST) was first introduced in Switzerland in 1977 and is now built by Swisslastic AG in St. Gallen. The MK V is the current model. It is one of a small number of instruments used to measure the pressure of compression stockings, and it appears throughout published research on medical compression hosiery, often used with the German RAL-GZ 387 test method.
How it works: the sock is pulled onto a leg-shaped form, the same way you'd put it on. Flat pressure sensors sit between the form and the fabric at fixed points along the leg. The machine reads the pressure at each point and prints a dated receipt showing every reading in mmHg, and each reading as a percentage of the ankle value.
That printout is our source of truth. It shows two things at once: whether the ankle pressure hits the target, and whether the pressure steps down the leg the way graduated compression should.
Our latest results: 15–20 mmHg knee-high, every size
These are the actual Swisslastic MST MK V readings from pre-production samples of our 15–20 mmHg nylon knee-high (rose/navy stripe), measured on September 19, 2026, before we approved the production run. Percentages show each reading relative to the ankle.
| Size | Ankle (b) | Lower calf (b1) | Calf (c) | Below knee (d) | Result |
|---|---|---|---|---|---|
| S | 20.0 mmHg | 16.7 (83.5%) | 15.0 (75.0%) | 13.1 (65.5%) | Pass |
| S Wide | 20.3 mmHg | 18.6 (91.4%) | 17.7 (87.0%) | 14.4 (70.8%) | Pass |
| M | 19.5 mmHg | 17.6 (90.3%) | 15.1 (77.4%) | 13.4 (68.7%) | Pass |
| L | 19.9 mmHg | 18.1 (91.0%) | 15.4 (77.4%) | 12.8 (64.3%) | Pass |
| XL | 20.3 mmHg | 17.4 (85.5%) | 16.5 (81.1%) | 13.6 (66.8%) | Pass |
What the numbers say: all five sizes landed between 19.5 and 20.3 mmHg at the ankle, at the firm end of the 15–20 range and inside our ±3 mmHg tolerance. Every size steps down at every point, finishing at roughly two-thirds of the ankle pressure below the knee. That consistency from S to XL is what we look for, because your size should change the fit, not the dose.
How does Comrad test compression socks? Our 6-step approval process
Testing isn't one step at the end. It runs through development and production.
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We write the spec first
Every style starts with a tech pack: target compression at the ankle, the gradient up the leg, fiber content, and exact dimensions for each size. Our size charts are built on ankle and calf circumference, the two measurements that decide where the pressure lands.
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We measure the development sample
The first samples go on the Swisslastic tester. We need the target pressure at the ankle and a clean step-down at every point above it. If the readout doesn't match the label, the sample goes back.
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We test every size before production
A Medium that passes doesn't prove an XL will. Before a production order is approved, pre-production samples in every size, including wide-calf sizes, are measured and checked against the spec.
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We check fit against measured tolerances
We measure cuff height and width, leg length, foot length, footbed width and stretch at the cuff, ankle, arch and forefoot against written tolerances for each size, unworn and after wear. Length matters more than it looks: a sock that runs long moves the firmest pressure off your ankle.
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We send samples to an independent lab
Pre-production samples go to SGS, an independent testing company, for pilling resistance and colorfastness. Our 2026 samples scored Grade 4.5 out of 5 on both. Our minimum is Grade 4.
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New compression levels clear a higher bar
When we develop a new compression level or fabric, we also require readouts in every size after repeated washing, wear-testing on real people with different leg shapes, and an independent lab report on the final approved sample to confirm the factory's numbers.
How to tell if a compression sock is really graduated
You can't measure pressure at home, but you can tell a lot about how seriously a brand tests. Before you buy any compression sock, check these four things:
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Look for an mmHg range, not just the word "compression"
A real compression sock states its pressure in mmHg, such as 15–20 or 20–30. If there's no number, there's no spec to test against. Not sure which level you need? Read what level of compression socks do I need.
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Check that sizing uses ankle and calf measurements
Pressure depends on how far the fabric stretches around your leg, so shoe size alone isn't enough. Here's how to measure for compression socks.
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Ask how the brand measures pressure
Brands that test can name the instrument and show readings at more than one point on the leg. A single number with no method behind it is a label, not a measurement.
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Feel for firmer pressure at the ankle
A graduated sock should feel snuggest just above your ankle bone and looser near the knee. If the band below the knee digs in more than the ankle, the gradient is likely off. See how tight compression socks should be.
The compression levels we make
Every level below goes through the same measurement process. Not sure which one is right for you? Compare 15–20 vs 20–30 mmHg, read Compression 101 or take the sock quiz.
Everyday comfort and lounging. Found in our Cozy Compression socks.
Shop 10–15 mmHgOur most popular level for long shifts, travel and all-day wear, in nylon and CloudCotton knee-highs.
Shop 15–20 mmHgMore support for heavier, tired legs and long days on your feet, in CloudCotton knee-highs and calf sleeves.
Shop 20–30 mmHgWhat lab testing can't tell you
A leg form is a standard, not your leg. The pressure you feel depends on your ankle and calf measurements, which is why sizing matters as much as the sock. Please measure before you order using our size chart.
Different testing devices can report slightly different numbers for the same sock, so we compare results on the same method over time. Compression also relaxes as fabric wears; follow the care label and replace socks when they lose their snap.
Compression socks aren't a substitute for medical care. If you have a circulation condition, diabetes with reduced sensation, or swelling with no known cause, talk to a clinician before wearing compression. Read our safety and use guidance.
Compression testing, answered
How does Comrad test its compression socks?
Our factory partners measure every compression style on a Swisslastic MST MK V medical stocking tester. The sock is pulled onto a leg-shaped form and the machine reads pressure in mmHg at four points: the ankle (b), lower calf (b1), calf (c) and just below the knee (d). We check every size against our spec before approving production, and send pre-production samples to SGS for pilling and colorfastness testing.
What is a Swisslastic MST MK V?
It's a medical stocking tester made by Swisslastic AG in St. Gallen, Switzerland. The MST was first introduced in 1977 and the MK V is the current model. It measures the pressure a compression garment applies at set points on a standardized leg form and prints the results, and it's widely used in research on medical compression hosiery.
What does "graduated compression" mean?
The sock is firmest at the ankle and gets gradually lighter up the leg. In our latest 15–20 mmHg readouts, pressure below the knee measured about 64–71% of the ankle pressure across all sizes.
Do you test every size?
Yes. Before a production order is approved, pre-production samples in every size, including wide-calf sizes, are measured on the tester. Our latest 15–20 mmHg knee-high read 19.5–20.3 mmHg at the ankle across S, S Wide, M, L and XL.
How accurate is the compression level on the label?
We hold the ankle reading to within ±3 mmHg of the labeled range, and the pressure must decrease at every point up the leg. A sample that misses either test is rejected and remade.
Are Comrad socks "medical grade"?
"Medical grade" isn't a single certification in the U.S. Rather than lean on that phrase, we publish how we measure and what the measurements show. Our socks are graduated compression socks made to a measured spec. They are not a substitute for medical care.
Does compression wear off after washing?
All compression fabric relaxes over time. Washing on gentle or cold and air-drying helps socks hold their pressure longer (our washing guide). For new compression levels and fabrics, we require pressure readouts after repeated washing before we approve them.
How can I tell if compression socks are really graduated?
Check for a stated mmHg range, sizing based on ankle and calf measurements, and a brand that can name its testing instrument and show readings at more than one point on the leg. On your leg, a graduated sock feels snuggest just above the ankle and looser near the knee.
Socks you can trust, measured to prove it
Graduated compression, tested in every size, built to look good on long days.