The material guide
Underwear materials, without the marketing fog
Modal and bamboo are not interchangeable labels. Organic cotton does not inherently dry faster than cotton. Microfiber is a size, not one fiber. Here is what each material means, what it tends to do well, and how brands using it score on this site.
9 material families · 40 brands · Updated August 2026
The short answer
Choose by the tradeoff you care about
Softest hand
Modal or MicroModal
Prioritize fabric feel and low bulk.
Familiar everyday feel
Cotton
Easy to understand, absorbent, and widely available.
Fastest drying
Polyester or nylon
Best suited to workouts, travel, and frequent washing.
Multi-day wear
Merino wool
Strongest case for temperature and odor management.
Compare
Every material at a glance
Score averages are calculated from matching brands, not isolated fabric swatches. A brand can appear in more than one row because most sell multiple collections and blended fabrics.
| Material | Typical feel | Drying | Plastic content | Comfort | Breathability | Durability | Brands |
|---|---|---|---|---|---|---|---|
| Modal & MicroModalRegenerated cellulose | Silky, light, very soft | Medium | Base fiber: no · stretch blends often contain elastane | 8.9 | 8.4 | 8.0 | 19 |
| CottonPlant fiber | Familiar, soft, more structured | Slow | Base fiber: no · stretch blends may contain synthetics | 8.3 | 7.9 | 7.9 | 21 |
| Organic cottonPlant fiber · certified subset | The same range as conventional cotton | Slow | Base fiber: no · check elastane and waistband construction | 8.6 | 7.6 | 7.7 | 4 |
| Viscose & rayonRegenerated cellulose | Smooth, drapey, soft | Medium | Base fiber: no · blends frequently add nylon or elastane | 8.7 | 8.5 | 7.8 | 5 |
| LyocellRegenerated cellulose | Smooth, soft, lightly structured | Medium | Base fiber: no · underwear blends often add synthetics | 9.1 | 9.2 | 8.0 | 2 |
| Polyester & microfiberSynthetic plastic fiber | Smooth to slick; highly construction-dependent | Fast | Yes · recycled polyester is still polyester | 8.4 | 8.2 | 8.2 | 15 |
| Nylon & polyamideSynthetic plastic fiber | Smooth, close, sometimes slick | Fast | Yes · polyamide is nylon | 8.6 | 8.8 | 8.0 | 10 |
| Merino woolAnimal protein fiber | Soft when fine; never as slick as modal | Medium | Base fiber: no · corespun blends often contain nylon | 9.0 | 9.1 | 7.9 | 3 |
| SilkAnimal protein fiber | Very smooth, light, luxurious | Care-dependent | Base fiber: no · blends and elastic components vary | 9.2 | 8.2 | 8.7 | 1 |
The full guide
Material by material
Regenerated cellulose
Modal & MicroModal
Wood-derived cellulose dissolved and regenerated into a very fine fiber. MicroModal describes an especially fine version, not a different raw material.
- Moisture and heat
- Absorbent; comfortable when lightly damp
- Typical drying
- Medium
- Typical durability
- Medium
- Average pair
- $26 · n=19
Best for
Soft everyday wear, fitted trousers, and warm sleepers
Watch for
Ultra-light knits can trade abrasion resistance for softness.
Plant fiber
Cotton
The familiar underwear baseline: naturally absorbent, easy to wash, and highly dependent on staple length, yarn quality, knit, and finishing.
- Moisture and heat
- Absorbs well; can stay wet once saturated
- Typical drying
- Slow
- Typical durability
- Medium-high
- Average pair
- $22 · n=21
Best for
Everyday wear, sensitive-feeling skin, and easy laundering
Watch for
Standard cotton jersey is rarely the fastest option after heavy sweat.
Plant fiber · certified subset
Organic cotton
Still cotton in wear terms. The meaningful difference is how the fiber is grown and verified; GOTS and OCS claims should name their scope rather than act as a vague green badge.
- Moisture and heat
- The same absorbent behavior as cotton
- Typical drying
- Slow
- Typical durability
- Medium-high
- Average pair
- $19 · n=4
Best for
Buyers prioritizing certified organic fiber and a cotton hand
Watch for
The word organic alone does not prove a finished-garment certification.
Regenerated cellulose
Viscose & rayon
Plant cellulose converted into a manufactured fiber. Products sold as bamboo underwear are usually viscose or rayon made using bamboo as the cellulose source.
- Moisture and heat
- Absorbent; performance varies by knit
- Typical drying
- Medium
- Typical durability
- Variable
- Average pair
- $18 · n=5
Best for
Soft basics when modal pricing is unnecessary
Watch for
Bamboo is a feedstock claim, not the generic fiber name or an automatic environmental benefit.
Regenerated cellulose
Lyocell
Another wood-derived regenerated cellulose. It is related to modal but made through a different solvent process and often feels slightly more substantial.
- Moisture and heat
- Absorbent and comfortable next to skin
- Typical drying
- Medium
- Typical durability
- Medium-high
- Average pair
- $50 · n=2
Best for
Soft performance blends and temperature-variable wear
Watch for
TENCEL is a branded fiber; it does not describe every finish or component in the garment.
Synthetic plastic fiber
Polyester & microfiber
A durable, low-absorbency synthetic widely used in performance knits. Microfiber describes very fine filaments and can also be nylon, so always read the fiber label.
- Moisture and heat
- Low absorbency; wicking depends on knit and finish
- Typical drying
- Fast
- Typical durability
- High
- Average pair
- $24 · n=15
Best for
Training, quick drying, rough wash cycles, and travel
Watch for
Synthetic textiles can shed plastic microfibers during wear and washing.
Synthetic plastic fiber
Nylon & polyamide
Two names for the same broad synthetic-fiber family. Underwear brands use it for strength, stretch recovery, smoothness, and light mesh structures.
- Moisture and heat
- Low absorbency; works well in open knits
- Typical drying
- Fast
- Typical durability
- High
- Average pair
- $25 · n=10
Best for
Sport, travel, mesh ventilation, and high-friction use
Watch for
Like polyester, it is a plastic fiber and can shed synthetic microfibers.
Animal protein fiber
Merino wool
Fine wool used in travel and performance underwear for moisture-vapor management, temperature regulation, and odor resistance between washes.
- Moisture and heat
- Manages vapor well and buffers temperature changes
- Typical drying
- Medium
- Typical durability
- Medium
- Average pair
- $48 · n=3
Best for
Multi-day travel, hiking, changing temperatures, and odor control
Watch for
Fine merino can thin at friction points and needs gentler care.
Animal protein fiber
Silk
A fine natural filament used here mainly in luxury underwear. Its appeal is hand feel and low bulk rather than hard-wearing performance value.
- Moisture and heat
- Comfortable in light wear; construction matters
- Typical drying
- Care-dependent
- Typical durability
- Delicate
- Average pair
- $80 · n=1
Best for
Luxury, lounging, and low-bulk wear
Watch for
Price, specialized care, and abrasion make it a niche daily option.
Read the label
Why almost every pair is a blend
Elastane, spandex, and Lycra
Elastane and spandex are two names for the same stretch-fiber category; Lycra is a brand name. A small percentage helps a pouch, waistband, and leg opening recover, but it also means a nominally natural or cellulosic pair may not be plastic-free.
Mesh, microfiber, and trade names
Mesh describes construction, microfiber describes filament size, and names such as AIRism or AIRKNITx identify a branded fabric. None tells you the underlying fiber content by itself. The sewn-in label is the useful part.
Microplastics
Plastic fiber and chemical-safety certification are different questions
Polyester and nylon are synthetic plastic fibers, and wearing and washing synthetic textiles can release plastic microfibers. Modal, viscose, lyocell, cotton, wool, and silk are not plastic base fibers—but a finished pair may still contain elastane, nylon cores, synthetic waistbands, or trims. OEKO-TEX STANDARD 100 tests textiles for harmful substances; it is not a plastic-free certification.
Method note — Material score averages reuse the provisional brand-level scores already published across Underwearank. They are useful for seeing this dataset, not for proving that a fiber causes a score. Knit, yarn, weight, blend, finish, pattern, and construction can matter as much as the fiber name.