This is the least balanced comparison in outdoor clothing. Cotton is comfortable, cheap and fine for warm, dry, low-effort days. In cold or wet conditions it is genuinely hazardous, and the reason is physical rather than a matter of preference. If you are choosing between the two for anything active in cool weather, choose merino — our base layer tops exist for exactly this situation.
The comparison at a glance
| Property | Merino wool | Cotton |
|---|---|---|
| Behaviour when wet | Keeps loft and much of its insulation | Collapses, holds cold water against skin |
| Drying speed | Moderate | Very slow — the core problem |
| Warmth for the weight | High | Low, and near zero once damp |
| Odour over repeat wears | Several wears | One wear, sometimes less |
| Comfort in dry heat | Good in light weights | Excellent — cotton’s real strength |
| Durability | Moderate; pills at wear points | Good, and tolerates hot washing |
| Price | High | Low |
| Care | Cool wash, dry flat | Tolerates almost anything |
Why wet cotton is a safety problem
Cotton fibres absorb large amounts of water and lose their structure when they do. The fabric flattens, the air pockets that provide insulation disappear, and what remains is a layer of cold water held directly against skin. Water conducts heat away from the body far faster than air, so a wet cotton shirt actively removes heat rather than merely failing to retain it.
It also dries very slowly. A damp cotton t-shirt worn under a shell on a winter hike can stay damp for the entire day, cooling you continuously. This is why mountain safety instruction has long warned against cotton for cold-weather activity, and why hypothermia cases so often involve someone in ordinary clothes who got wet and stayed out.
Where merino behaves differently
Wool absorbs moisture into the fibre rather than into the spaces between fibres, so the knit keeps its structure. The natural crimp holds the fabric open and continues trapping air even when the wool itself is damp. Insulation drops, but it does not vanish.
Merino also moves vapour before it becomes liquid. During stop-start effort — the pattern of almost every hike, ski tour and winter commute — that means less accumulated moisture to deal with in the first place.
Where cotton is the better choice
Cotton earns its place in dry heat. It absorbs sweat and holds it against the skin, and in hot dry conditions that evaporative cooling is exactly what you want. A cotton shirt on a hot summer afternoon in the Okanagan is more comfortable than merino for the same reason it is dangerous in February.
- Hot, dry, low-effort days. Cotton is genuinely more pleasant.
- Everyday indoor wear. There is no reason to spend on merino for a shirt worn in a heated office.
- Hard-wearing work clothing. Cotton canvas and denim tolerate abuse that would destroy fine wool.
- Anything you will wash hot. Cotton survives laundry habits that ruin wool.
The cost argument, examined properly
Cotton is far cheaper per garment, and that is a real consideration. The comparison changes somewhat over a garment’s life: merino is worn more times between washes, and fewer wash cycles means slower wear. A merino base layer worn four times per wash goes through roughly a quarter of the laundry cycles of a cotton shirt worn once.
That does not close a four-fold price gap for most people, and pretending otherwise would be dishonest. The stronger argument for merino is not economy but capability — it does something cotton cannot do in cold, wet, active conditions. Where that capability is irrelevant, cotton is the sensible purchase.
What about cotton blends and treated cotton?
A poly-cotton blend improves matters but does not solve them. The cotton content still absorbs water and still dries slowly; the polyester content simply reduces how much. A 50/50 blend behaves better than pure cotton in the wet and considerably worse than either pure synthetic or wool.
Treated and technical cottons make similar partial gains. They are worth having if cotton is what you own, and they are not a reason to choose cotton for cold-weather activity when better options exist at similar prices.
What to wear instead of cotton
For hiking and travel, a light merino top in the 150–190 gsm range replaces a cotton t-shirt directly and packs smaller. For cold conditions, add weight rather than layers of cotton — our weight guide covers the ranges.
Socks deserve particular attention, because cotton socks are the most common cause of blisters on a hike. Cotton holds sweat against the foot and softens skin, which is precisely the condition friction needs to create a blister. Merino hiking socks are the single highest-value swap most people can make.
For a full comparison against the other common base-layer material, see merino versus synthetic base layers, and merino for hiking for putting a kit together. Browse base layers to compare weights.
Related merino guides
Sources
Image: Merino Mart catalogue. Browse base layer tops.