The Fabric Bible: What Your Briefs Are Actually Made Of

Cotton, modal, merino, bamboo and the synthetics compared. The best fabric for men's underwear comes down to staple length, knit and the label's small print.

By Keith · 27 July 2026 · 10 min read

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Two briefs can be ninety five percent cotton and five percent elastane and be completely different garments. One is soft, holds its shape for years and disappears under a trouser. The other pills within a month, goes baggy by lunchtime and is grey by Easter. Same label, same percentages, same price bracket.

The label is telling you what the fibre is. It is not telling you how long the fibre is, how it was spun, or how it was knitted, and those three things decide almost everything about how the finished garment behaves. This article is about the part of the story the label leaves out, fibre by fibre, plus the knit structures that matter and the numbers actually worth reading.

Cotton, and the enormous range hiding inside one word

Cotton is the default for good reasons. It is soft, it breathes, it takes dye well, it can be washed at temperatures that kill things, and human beings have been refining it for a very long time.

The variable nobody explains is staple length, which is the length of the individual fibres before spinning. Ordinary upland cotton has a staple of roughly two and a half centimetres. Extra long staple varieties, sold as Supima in the United States, Giza in Egypt and Sea Island in the Caribbean, run to around three and a half centimetres or more.

Longer fibres matter because a yarn spun from them has fewer loose ends per centimetre. Fewer ends means a smoother surface, a stronger yarn, less pilling and considerably less of the fuzzy grey degradation that makes cheap cotton look tired after two months. It is why an expensive cotton brief still looks new after three years and a supermarket one does not survive a summer.

Combed cotton is the next thing to look for and is a separate claim. Combing is a mechanical process that removes the shortest fibres and aligns the rest before spinning. It throws away up to a fifth of the raw material, which is exactly why it costs more, and it produces a yarn that is noticeably smoother than carded cotton at the same staple length.

Mercerised cotton has been treated with caustic soda under tension, which swells the fibre, makes it rounder, and gives it a mild lustre plus better dye uptake and strength. It is common in higher end European briefs and is part of why a Swiss pair has that faint sheen.

The practical instruction is simple. If the label says only "cotton", assume the cheapest available. If it says combed, long staple, Supima or Egyptian, somebody has spent money in the one place where spending it visibly pays off Supima cotton brief.

Cotton's real weakness is water. It absorbs up to about a quarter of its own weight in moisture and holds onto it, which is fine at a desk and unpleasant on a hot walk or in a gym The Sweat Article: Moisture-Wicking Fabrics, Explained Properly.

Modal and micro-modal, the upgrade most men notice immediately

Modal is a regenerated cellulose fibre, which means it starts as wood pulp, usually beech, and is chemically reconstituted into a filament. It is not synthetic in the polyester sense and it is not natural in the cotton sense. It occupies its own category and it is the fibre most likely to make somebody say the words "why is this so much better".

What it does well is drape and softness. Modal has a smoother surface than cotton and a lower friction coefficient, so it feels cool and slippery against skin and moves against a trouser lining rather than gripping it. It absorbs around fifty percent more moisture than cotton and releases it faster, so it feels drier in warm weather despite technically being more absorbent.

It also holds colour extremely well and resists the mineral build up from hard water that turns white cotton grey.

Micro-modal is the same fibre spun finer, typically at or below one decitex, which means more filaments per unit of yarn and a softer, lighter, more fluid fabric. It is the fabric behind most of the premium comfort briefs sold in the last decade, and it is genuinely lovely.

The trade offs are real and rarely mentioned. Modal is weaker when wet than cotton, so it needs a gentler wash. It pills more readily than long staple cotton unless it is blended. And it is not a hot weather miracle: it feels cooler than cotton but it does not wick like a synthetic, so for actual sport it is the wrong tool micro-modal brief.

Lyocell, usually sold as Tencel, is a cousin made with a closed loop solvent process that recovers over ninety nine percent of its chemicals, which makes it the most environmentally defensible of the cellulosics. It is stronger than modal, especially wet, slightly less soft, and manages moisture better. If you see a lyocell blend at a reasonable price, it is usually the smart buy.

Bamboo, and a small honest correction

Bamboo underwear is sold on the strength of the plant, and the plant is largely irrelevant to the finished garment.

Almost all bamboo fabric is bamboo viscose, which means the bamboo has been dissolved in a chemical process very similar to the one used for any other viscose and emerges as regenerated cellulose. The original plant structure, and with it any of the antibacterial properties bamboo is marketed on, does not survive the process. Regulators in several countries have taken action against brands claiming otherwise.

That is not a reason to avoid it. Bamboo viscose is soft, drapes well, is often good value and behaves broadly like a slightly less refined modal. It is just a reason to buy it for what it is rather than for the story on the packet, and to prefer bamboo lyocell if you can find it, since that uses the cleaner closed loop process.

Merino, and why it is not itchy any more

Wool in underwear sounds like a punishment and is one of the best ideas in the drawer.

Merino is defined by fibre diameter, measured in microns. Traditional coarse wool sits above thirty microns and is what everybody remembers from a childhood jumper. Merino used in next to skin garments is typically seventeen to nineteen microns, and below about twenty two microns the fibre is fine enough to bend against skin rather than press into it, which is exactly why the itch disappears.

What merino does that nothing else does is manage moisture as a vapour. It can hold around a third of its weight in water inside the fibre while still feeling dry to the touch, which is why it stays comfortable across a much wider range of conditions than any other fibre. It also resists odour to a degree that reads as implausible until you have worn a pair for three days walking, and that is a genuine property of the fibre's structure rather than a treatment that washes out.

The costs are that it is expensive, it is slower to dry once genuinely soaked, and pure fine merino is fragile in a garment that gets this much abrasion. Look for a blend, typically merino with a nylon content of ten to twenty percent for durability plus a little elastane for recovery merino wool brief.

Merino is the correct answer for travel, for hiking, and for anyone who has to be presentable at the end of a long day in warm conditions Travel Light: The One-Bag Case for Briefs.

The synthetics

Polyamide, which is nylon, is the workhorse of performance underwear. Strong, abrasion resistant, quick drying, excellent stretch recovery, and softer than polyester. Most good sports briefs are a polyamide and elastane blend.

Polyester is cheaper, dries even faster, and holds odour badly because its surface chemistry positively welcomes the bacteria responsible. Antimicrobial treatments help and most of them wash out over time.

Elastane, also sold as Lycra and spandex, is not a fabric in its own right, it is the recovery mechanism. Percentages are worth understanding. Two to three percent gives shape retention with a natural hand. Five percent is the everyday standard for a brief and the right answer most of the time. Eight to twelve percent produces a compressive, second skin fit that suits sport and runs warm. Elastane is also the component that fails first in almost every garment, and it is destroyed by heat, chlorine and fabric softener, which is why all three should stay away from your drawer.

Bonded and laser cut synthetics are the modern invisible option: no seams, no hems, raw edges sealed by heat. They genuinely disappear under close trousers. They also fail all at once rather than gradually, and they are a poor choice in real heat.

The knit, which is the half of the story nobody mentions

Two garments in identical fibre can behave completely differently because of how the yarn is looped.

Single jersey is the basic knit: smooth face, looped back, light, cheap, and prone to curling at cut edges. Most inexpensive briefs are single jersey.

Rib alternates columns of face and reverse stitches, which gives the fabric enormous lateral stretch and, crucially, mechanical recovery that does not depend on elastane. A good cotton rib holds its shape through elastane failure, which is why the classic German fine rib brief is such a durable object. The trade is that it is a slightly heavier, more textured fabric Schiesser fine rib brief.

Interlock is two rib fabrics knitted together, producing a smooth, stable, identical faced fabric with excellent shape retention and real substance. It is what the Swiss houses use and part of why their garments feel like they were made to a specification rather than a price. Whether that specification justifies the price at the very top of the Swiss shelf is a separate argument. Is Zimmerli Actually Worth It?

Mesh and open knits exist for airflow and do exactly what they suggest, at the cost of opacity.

Fabric weight, given in grams per square metre, is the other number worth knowing when a brand publishes it. Below about 140 is summer weight and will be light and slightly translucent. From 150 to 180 is the everyday range. Above 200 is heavyweight and superb in winter and miserable in August The Winter Base Layer: How to Be Warm Without Looking Like a Bin Bag.

What to actually buy

For most days of most years, combed or long staple cotton with about five percent elastane, knitted as a rib or interlock rather than a plain jersey. Nothing has beaten this and nothing is likely to.

Under tailoring, and for anyone who cares about how the garment reads through a fine trouser, micro-modal, because it drapes closer than cotton and does not grip a lining Briefs for the Office: The Tailoring Argument.

For travel, walking, and multi day wear, merino blended with nylon.

For actual sport, polyamide with eight to twelve percent elastane and flatlock seams Right Support, Right Sport: What to Wear for What You Do.

For heat, a light cotton rib or a lyocell blend, and nothing above about 150 grams per square metre.

That is five fabrics for five jobs, and a drawer built around three of them will handle everything most men do The Drawer Audit: How Many Briefs You Need and When to Replace Them.

Knowing what the fibres do is half the job. The other half is reading what the packaging says about them, since a great deal of the language on an underwear pack describes a finish that washes out rather than a fibre that does not Moisture-Wicking, Antibacterial, Four-Way Stretch: What the Claims Actually Mean.

Questions people ask

What is the best fabric for men's briefs?

For everyday wear, combed or long staple cotton with around five percent elastane, ideally knitted as a rib or interlock rather than plain jersey, because that combination gives you breathability, softness and shape retention at a sensible price. Micro-modal is the better choice under tailoring, merino is the better choice for travel and long days, and polyamide with a higher elastane content is the better choice for sport.

Is modal better than cotton for underwear?

For softness, drape and how the garment reads under close fitting trousers, yes. Modal is smoother, moves against a lining rather than gripping it, absorbs more moisture than cotton and releases it faster, and resists the greying that hard water inflicts on white cotton. Cotton is more durable, cheaper, tolerates hot washes better and is the more sensible everyday default. Modal is an upgrade in comfort rather than in longevity.

Is bamboo underwear actually antibacterial?

No. Almost all bamboo fabric is bamboo viscose, which means the plant has been chemically dissolved and reconstituted, and the antibacterial properties of the raw bamboo plant do not survive that process. Several regulators have acted against brands that claimed otherwise. Bamboo viscose is still soft, well draping and often good value, so buy it for what it is rather than for the marketing.

How much elastane should briefs have?

Around five percent is the everyday standard and the right answer for most cotton briefs, giving shape retention without a compressive feel. Two to three percent suits a good rib knit, which recovers mechanically anyway. Eight to twelve percent is performance territory, fitting like a second skin and running warmer. Whatever the number, elastane is the component that dies first, and heat, chlorine and fabric softener all kill it faster.

Does merino wool underwear itch?

Not at the fibre diameters used for next to skin garments. Itch is a function of how thick each fibre is, and anything below about twenty two microns bends against the skin instead of pressing into it. Merino used in underwear is typically seventeen to nineteen microns, which is finer than the threshold and does not itch. The scratchy wool people remember from childhood jumpers is usually above thirty microns.

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