UK vs US size grading: why your tech pack must say which

The most expensive ambiguity in a tech pack is usually a single letter. “Medium” means one set of measurements to a UK brand, another to an American one, and something else again to a factory that mostly runs a domestic size set.

Nobody notices until the sample arrives, and then it costs a round.

Letters and numbers do not travel

Two separate problems:

Womenswear numbering differs between markets. UK and US dress sizes are numbered on different scales, so the same physical garment carries different numbers in each. There is a conventional offset between them, and it is not reliable enough to build a range on — it varies by brand, by category and over time, because of vanity sizing.

Letter sizes look universal and are not. S/M/L/XL are used everywhere, and the measurements behind them differ by market and by brand. A US medium tee is typically cut broader than a European one; a UK brand’s medium may sit somewhere between.

The conclusion is the same in both cases: the letters and numbers are labels, not specifications.

Send measurements

The only unambiguous instruction is a size chart in centimetres, with the points of measure named.

For a knit tee, at minimum:

Point of measure	Why it is there
Chest, 2.5 cm below armhole	The primary fit dimension
Body length from high point shoulder	Decides whether it reads cropped, regular or long
Shoulder seam to seam	Sets where the shoulder sits
Sleeve length from shoulder seam	And whether it is measured from the seam or the neck
Sleeve opening	Often forgotten, very visible
Neck opening or rib width	Where a lot of “it looks cheap” comes from
Hem width	Whether it is straight or tapered

Name the method as well as the number. “Sleeve length 21 cm” means two different things depending on where you started measuring, and a factory will pick one.

Grading is a separate decision

The base size gets attention. The grade — how much each measurement grows between sizes — often does not, and it decides whether your XL customer gets a garment that fits or a scaled-up medium.

Two things to state:

• The grade rule per point of measure. Chest might grow 5 cm per size while shoulder grows 1.5 cm and body length 2 cm. They do not all grow at the same rate.
• Where the grade changes. Many ranges grade differently at the top end, because bodies are not linear.

If you do not specify, the factory applies a house grade. That is not negligence — it is the only thing they can do — but it means your size run is somebody else’s default.

Men’s, women’s and unisex are different blocks

A women’s tee is not a small men’s tee. The armhole, shoulder slope, neck opening and body shaping all differ, and grading a men’s block down produces a garment that fits nobody well.

“Unisex” is a real block, not a compromise — it is usually a men’s-derived block with adjusted proportions, and it should be specified as such rather than assumed.

Say explicitly which block each style uses. It is one line and it removes a whole class of sampling failure.

Tolerances, or the inspector has nothing to check

Every measurement needs a tolerance, because garments are cut and sewn rather than machined. Typically a tolerance is tighter on chest than on length, and tighter on a fitted style than on an oversized one.

Without stated tolerances, a pre-shipment inspection cannot assess measurements at all — it is one of the things an AQL inspection checks, and “it should match the sample” is not something anyone can measure.

Get a signed sealed sample with the measurement chart and tolerances attached. That document, not the email thread, is what a dispute gets resolved against.

Fabric moves the numbers

A cut-and-sew measurement is not the finished measurement. Knitted fabric relaxes, shrinks and recovers, and how much depends on the fibre, the weight and whether it was compacted and pre-shrunk before cutting.

This is why an uncompacted fabric produces garments that measure correctly at the factory and wrong after the customer washes them. What the fabric specification actually decides includes this, and it is a sizing problem as much as a quality one.

For a stretch fabric, state whether the measurement is relaxed or extended. They are very different numbers.

Do it before sampling

Regrading after a fit sample costs a full sampling round — typically 7–10 working days plus your own approval time, on top of whatever the range already needed.

Deciding the system, the chart and the tolerances before the first sample is perhaps an hour of work. It is the cheapest hour in the whole process, and one of the reasons a supplier who has shipped to your market before is worth something — as covered in choosing a manufacturer for a UK brand.

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We grade to UK size sets as standard for UK buyers, and we will work from your own chart and tolerance table if you have one — send it with your tech pack. If you do not have one, send a garment that fits the way you want and we will pattern from it. Programmes start at 300 pieces per style per colour — talk to us about a range.