Every compression sock guide tells you 15-20 mmHg is for travel and 20-30 is medical grade. Almost none of them can help you with the questions that follow in a buying conversation: what physically differs on the knitting machine, why the firmer grade costs more to make and certify, and which grade a retail program should actually launch with. Those are manufacturing questions, and they change the quote, the SKUs, and the compliance path — this guide answers them from the production side.
Quick answer: the two grades are knit to different pressure tolerances. 15-20 mmHg is a retail comfort product — the gradient is achieved with elastic yarn ratio and forgiving tolerance bands, it sells as ordinary apparel, and it is the right first launch for most consumer brands. 20-30 mmHg is held to tighter pressure points at the ankle and calf, needs batch pressure testing with reports to sell credibly into medical channels, and carries a wider size matrix because pressure delivery depends on fit. If your customers are nurses on twelve-hour shifts, you can serve them well with 15-20. If you are selling post-surgical recovery, you are in 20-30 territory with documents to match.
What the Numbers Physically Mean on the Machine
mmHg readings are graduated — strongest at the ankle, easing up the calf. Two production levers create the gradient: stitch density programming (zones knit tighter or looser) and the elastic yarn's power and ratio. At 15-20, both levers run in comfortable bands; minor variation stays inside the tolerance. At 20-30, the ankle zone pushes toward the top of the elastic's working range, which means fit circumference now matters to whether the customer receives the stated pressure — and the knitting has less room for drift. That is why serious 20-30 programs run pressure testing on production batches, with reports, and why a size chart for a firm-grade sock is a engineering document, not a suggestion. Our medical compression sourcing page covers what to specify when you order this grade.
The Cost Structure Nobody Puts on the Label
The price gap between grades is not markup — it is three cost lines. Testing: firm-grade credibility requires pressure verification per batch; labs charge per style per size, and the size matrix is larger (pressure delivery depends on fit, so "one size" is a retail luxury that medical channels do not accept). Yield: tighter tolerance means more pairs pulled at QC. Certification boundary: in most markets, 15-20 sells as ordinary textile apparel with standard fiber-content labeling. The moment a product claims a therapeutic effect, or is marketed into post-surgical channels, you cross into regulated territory — different paperwork, different claims review, occasionally a different distribution channel entirely. The certifications guide covers how to verify the documents either way; the decision here is which side of the line your program lives on.
Which Grade Should a Retail Brand Launch With
For a private-label or studio-branded program, 15-20 is almost always the right first product, for three manufacturing-grounded reasons. First, the compliance path is ordinary apparel — no therapeutic claims, no medical-channel paperwork, listings sell on comfort language ("all-day support," "travel") that regulation tolerates. Second, wearability drives reorders: the softer grade gets worn daily and washed without drama, while firm grades suffer a comfort dropout curve that shows up in your review section. Third, the size matrix can start small — one or two sizes cover most wearers at 15-20, versus the four-to-six size graduations a responsible 20-30 program carries.
Launch 20-30 when your channel demands it: medical supply retail, post-surgical referral partnerships, occupational programs with a clinical supervisor involved. Then budget for the pressure test reports up front — they are the product's spine, and the MOQ economics of testing fees across a wide size matrix is part of the real unit cost.
The Grey Zone Claims That Get Brands in Trouble
The repeat offender is language. "Improves circulation" on a 15-20 sock is a therapeutic claim on a non-therapeutic product — platforms flag it, and in regulated markets it invites a claims review. The safe frame for retail grade is comfort and fatigue language; the pressure number may be stated, the medical outcome may not be promised. Brands that want both worlds often run two SKUs: the retail grade sells freely, the firm grade carries its test reports into channels equipped to use them. Two SKUs is more work; one mislabeled SKU is more risk.
FAQ
Is 20-30 mmHg always better than 15-20? No. The grades serve different jobs. 15-20 is the daily-wear comfort grade with an ordinary-apparel compliance path; 20-30 is a firmer, tolerance-critical product whose value depends on testing and correct sizing. Better depends on the channel you are selling into.
Do I need pressure test reports for 15-20 mmHg socks? Not to sell them as apparel. If you plan to print the pressure range, having the test on file is good practice for customer service and platform questions, but the compliance burden differs enormously from therapeutic-grade products.
Why do 20-30 mmHg socks come in more sizes? Because delivered pressure depends on the sock's stretch relative to the wearer's leg. A firm grade needs tighter fit matching to hit its stated pressure window, so responsible programs grade more sizes — which is also part of why the grade costs more per SKU.
Can one factory make both grades? Gradient knitting is a standard capability, but ask for the pressure testing arrangement specifically — batch testing with reports is the part that separates medical-grade suppliers from general knit mills.
What claims can I put on my 15-20 mmHg listing? Comfort framing: support, fatigue, travel, all-day wear. Avoid therapeutic outcomes ("treats," "improves circulation," "prevents DVT") unless you are prepared for the medical claims path in your market.
Are gradient and anti-embolism socks the same thing? No. Anti-embolism stockings are a specific medical product category with its own standards, used for immobile patients. Retail "gradient compression" describes the ankle-to-calf pressure slope in consumer products — related principle, different product class.