We earn a commission if you buy through links on this page, at no extra cost to you. How we earn.
Best thermal base layers to buy right now
Merino is the base layer to buy if you can afford it: it stays warm when damp and does not smell after a week of wear. Synthetic layers dry faster and cost a third as much, so they suit running and cycling where you sweat hard. Cotton is the one fabric to avoid.
-
Best for most people
1. Helly Hansen Lifa Stripe Crew
Aerobic activity · Long-sleeve crew · Polypropylene
The original synthetic base layer and the best seller among the branded ones here, made from polypropylene that moves sweat off your skin. It suits running, cycling and ski days where you work hard and need it to dry fast. Synthetic fabric holds smells more than merino, so it is less suited to several days of wear between washes.
-
Best merino set
2. Merino.tech Merino Base Layer Set
Superfine merino, 17.5 micron · 250 g/m², midweight · Top, long johns and socks
A full merino top and long johns, plus a pair of hiking socks, which is good value next to buying a branded merino top and bottoms separately. The listing quotes 17.5 micron merino at a midweight 250 g/m², with lighter and heavier versions sold too. It asks for hand washing and flat drying, which is more care than a synthetic layer needs.
-
Best value merino top
3. DANISH ENDURANCE Merino Thermal Top
18.5 micron · Merino with recycled polyamide · 180 GSM
A midweight top that is mostly merino, with recycled polyamide added for durability. The listing quotes 180 GSM, 18.5 micron fibres, raglan sleeves, flat seams and mulesing-free wool. It is a top only, so pair it with leggings for full cover.
-
Best premium merino
4. Icebreaker 175 Everyday Crew
Slim · Merino rib knit · Raglan
A merino layer from one of the best-known names in the fabric, in a stretchy rib knit with raglan sleeves and forward side seams. The listing is short on detail and gives no fibre content or care advice. It is a slim fit, so size up if you want it to sit loose under a shirt.
Out of stock on Amazon
Buy on eBay -
Best budget set
5. Roadbox Fleece Thermal Underwear Set
Flatlock · Fleece-lined synthetic · Top and bottoms
A no-name men's top and bottoms set with a fleece lining that sells well and costs little. The listing quotes moisture wicking, 4-way stretch and flatlock seams, but names no fabric content. A fleece-lined synthetic is warm for standing about, but less breathable than thin merino when you work hard.
-
Best budget for women
6. SIMIYA Women's Thermal Underwear Set
Polyester and spandex, fleece-lined · 4-way · Top and leggings
A no-name women's set of fleece-lined top and leggings that doubles as winter pyjamas. The listing gives the fabric as polyester and spandex, then talks about a wool moisture system, but there is no wool in it. Fine for school runs and cold evenings, less so for a long hill walk.
-
Best leggings
7. Under Armour ColdGear Leggings
Dual-layer, brushed inside · Stretch mesh · 4-way
Thermal leggings from Under Armour's cold-weather range, with a brushed inside for warmth and a smooth, fast-drying outside. The listing quotes stretch-mesh panels at the gusset and inseam for ventilation and 4-way stretch. They are leggings only, so pair them with one of the tops above.
Nothing matches those filters. Try fewer filters, or search for a brand like "MSI" or "Crucial".
How we rank
Ordered by how well each sells in its Amazon UK category, what the listing confirms (fit, materials, sizes, features), and price. We have not handled these products: the write-ups rest on what each listing states. Prices and stock are checked daily.
Prices are Amazon UK and eBay UK at the time we last checked; they move daily, so confirm on the retailer's page. We earn a small commission if you buy through our links, at no cost to you. It never changes the order. More about how we work.