Fabric Composition Labels Explained: What the Percentages Mean

The composition label is the most reliable line of text attached to any garment. Photographs are styled, descriptions are written by marketing, and price signals brand positioning — but fibre percentages are a regulated statement of what the thing is made of, and they predict a surprising amount about how it will feel, wash and age.

This guide explains how those labels are constructed and what each fibre family brings. It is the companion to how to judge clothing quality, which covers construction rather than materials.

How composition labels are written and ordered

Textile products made available on the market in Great Britain must be labelled with the name and percentage by weight of every constituent fibre, listed in descending order. That is a real legal requirement, not a convention, and it applies to online listings too — the composition should be available to you before you buy, not only on the tag inside the parcel.

Two details are worth knowing. Where a fibre accounts for up to five per cent of the total, or several fibres together account for up to fifteen per cent, they may be grouped as "other fibres" with their combined percentage, where they cannot easily be stated at the time of manufacture. And where a product has two or more components with different compositions — a lined jacket, a garment with a contrast panel — each component's composition must be given, which is why "shell", "lining" and "trim" appear separately.

Invented marketing fibre names cannot replace proper fibre names. If a listing describes the material only as a trademarked fabric technology, the real composition exists somewhere; a retailer that does not show it has made a choice.

Natural fibres and their trade-offs

Cotton is comfortable, breathable, absorbent and easy to launder. It creases readily, is weaker when wet in some constructions, and its quality varies enormously with staple length and how it is spun — which is why two 100% cotton shirts can be entirely different garments.

Linen is strong, highly breathable and cool, softening with use. It creases dramatically, which is either the point or a problem depending on your temperament.

Wool insulates when damp, resists odour, drapes well and recovers its shape after wearing, which is why tailoring is built on it. It is sensitive to heat, agitation and alkaline detergent — the combination that causes felting — and quality varies with fibre fineness and the animal it came from.

Silk is strong for its weight with a distinctive handle and drape, but is sensitive to sunlight, perspiration and alkalinity, and usually demands careful laundering.

Synthetics: strength, stretch and pilling

Polyester is strong, dimensionally stable, quick-drying, resistant to creasing and cheap. It breathes less well than natural fibres, can retain odour, and its surface holds pills once they form.

Polyamide (nylon) is stronger and more abrasion-resistant than polyester, which is why it appears in hosiery, linings and outerwear where wear resistance matters.

Acrylic mimics wool's warmth at lower cost and lower weight, but is notably prone to pilling and does not recover shape as wool does.

Elastane — also sold under trade names — provides stretch and recovery, and is almost always a small percentage of a blend. It is the fibre most sensitive to heat, so hot washing and tumble drying degrade it first, after which a garment stretches without returning. Small percentage, decisive effect.

Regenerated fibres like viscose and modal

Viscose, modal and lyocell are neither natural nor synthetic in the usual sense: they are made by chemically processing plant cellulose into a new fibre. They are grouped as regenerated cellulosics and behave as a family.

They are soft, drape beautifully and take colour well, which is why they are common in fluid dresses, blouses and linings. Their characteristic weakness is strength when wet — noticeably lower than cotton's for viscose in particular — which is why care labels for viscose garments are often restrictive and why they can shrink or lose shape after careless washing.

Modal and lyocell are produced by different processes and are generally more robust when wet than standard viscose, which is worth noticing on a label because the three are frequently spoken about as interchangeable and are not.

Blends: why small percentages matter

Blends exist to combine properties: cotton for comfort with polyester for stability, wool for warmth with polyamide for abrasion resistance, almost anything with elastane for stretch. A blend is not a compromise by definition.

But small percentages carry disproportionate consequences, and in two directions. Elastane at a few per cent dictates how the garment must be washed and how it will age, regardless of what the other 95% is. A modest proportion of a strong synthetic in a knitwear blend can noticeably increase pilling and change the handle.

Read a blend by asking what each fibre was added for, and whether the smallest number on the label is the one that will govern the garment's care and lifespan. That is usually where the answer is — and it is the number to keep in mind when calculating cost per wear.

Fabric weight, GSM and drape

Composition tells you what a fabric is made of; weight tells you what it will do. Weight is quoted in grams per square metre or in ounces, and it predicts opacity, drape, warmth and durability better than most published figures.

The same fibre at different weights produces entirely different garments: a lightweight cotton is a summer shirt, a heavy one is a workwear jacket. This is why a composition label alone cannot answer whether something will be transparent or clingy, and why a retailer publishing GSM is giving you genuinely useful information.

Where weight is absent, the fallbacks are the photographs — transparency in the studio shot, how the fabric falls, whether it holds a fold — and the garment measurements rather than the size label, as covered in clothing sizing charts.

Pilling, shrinkage and colour retention

Pilling happens when short fibre ends work loose and tangle. Construction matters more than composition: loosely spun yarns and loose knits pill sooner. Composition then decides what happens next — strong synthetics hold pills on the surface, while weaker natural fibres tend to shed them.

Shrinkage depends on fibre, construction and finishing. Untreated natural fibres and knits are most prone; a garment labelled as pre-shrunk has had that accounted for; heat is usually the trigger, which is why washing temperature and drying method matter more than detergent.

Colour retention depends on dye and finishing rather than on fibre percentages, so the label cannot predict it. What can: dark and highly saturated colours are more prone to visible fading and to crocking, where dye transfers by rubbing.

All three are governed in practice by what the care label permits, which is why it is worth reading before purchase rather than after — see care labels explained.

Matching composition to how you'll wear it

• Frequent-wash basics: stable, launderable fibres and constructions; check for elastane and plan to wash cool.
• Tailoring and structure: wool for recovery and drape; watch for high synthetic content that will not hold shape.
• Warm weather: breathable naturals; accept creasing in linen as a property rather than a fault.
• Activity and abrasion: polyamide or polyester where wear resistance matters more than breathability.
• Fluid drape: regenerated cellulosics, with attention to their care restrictions.
• Anything you expect to keep for years: favour compositions and constructions that tolerate ordinary laundering, and apply the construction checks in how to judge product quality online.