I’ve been researching the warmest wool products available. Here’s what I discovered:

Qiviut (Musk Ox Down)

Qiviut (pronounced “kiv-ee-ute”) is the name for the downy hair of the musk ox. It is the warmest fiber in the world — about eight times as warm as sheep’s wool.

Musk oxen live in Alaska and Canada where temperatures sometimes drop to –100ºF (-73ºC), so they need protection. The Inuktitut name for the musk ox is “umingmak” meaning the “bearded one”.

Qiviut is an ultralight fiber and very soft fiber too. However, there is limited amount of Qivit produced every year, so it’s expensive.

In Alaska, qiviut is obtained from farmed animals or gathered from the wild during the molt. Unlike sheep, the musk ox are not sheared.

Qiviut Summary Extremely warm and light. A rare, soft and luxurious fiber.

Yak Down

Similar to qiviut, yak down is a very warm fiber that’s also lightweight and soft. It’s a more affordable alternative to the rare qiviut.

Yaks are primarily raised by nomadic Tibetan and Mongolian families. Their wool is combed once per year in the springtime.

According to Kora (a yak performance wear company) the wool is 40% warmer merino wool. It has 66% greater air permeability and 17% greater water vapor permeability (tested with ASTM D1518, ASTM D737, ASTM E96).

Yak Wool Summary Extraordinarily soft, warm and lightweight. Has some elasticity and bounce.

Bison Down

Bison down is a very warm, insulating fiber. It is also very durable for such a soft fiber. It has a moisture regain of about 30%, compared to 18% for sheep’s wool — this means that even when saturated, the fiber draws moisture away from one’s skin.

There is only a limited amount of fiber available – estimated at 10,000 pounds per year versus 2,100,000,000 pounds of sheep wool.



It is harvested in Colorado and South Dakota, as a by-product of the bison meat industry.

Bison Wool Summary A short and quite fine fiber that offers unusual durability for its level of softness.





Alpaca Wool

Alpaca wool is about three times as warm as sheep’s wool, and it is lightweight and durable. It contains no lanolin, which makes it hypoallergenic and odorless. Alpaca wool also has one of the highest moisture ‘wicking’ properties of all natural fibers.

Alpacas are kept in herds that graze in the mountains of Peru, Bolivia, Ecuador and Chile.

Alpaca Wool Summary Delightfully smooth, supple feel. Durable fiber. Not elastic.

Other Wools

Other warm (and very soft) wools include llama, camel, angora, cashmere, vicuna and guanaco.

Durability and Fineness

In terms of durability, bison is in most cases the strongest, followed by qiviut and yak down, alpaca and merino.

In terms of fineness, any fiber that has a diameter of 20µ (microns) or less will feel very soft to the touch. In the alpaca world, the labelled “royal” alpaca should indicate fibers under 19 µ, “baby” alpaca should indicate fibers that are around 22.5µ and “superfine” alpaca is 26µ.

There’s also an International Alpaca Mark that indicates the fibre is less than 28 µ.

In the merino world, look for wool labelled “ultrafine” (around 15-17 µ) or “superfine” (about 18-20 µ).

Here’s a list of fibers from finest to coarsest (in microns):

Vicuña (12µ)

Angora rabbit (8 – 12µ)

Suri Alpaca (10 – 15µ)

Silk (10 – 13µ)

Qiviut (11-13 µ)

Cashmere Goat (14 – 19µ)

Huacava Alpaca (15 – 29µ)

Camel (15 – 22µ)

Ultrafine Merino (15.5µ or less)

Yak Down (17.5 to 19µ)

Bison (14 -18µ)

“Royal” Grade Alpaca (19µ or less)

“Cashllama” Grade Llama (20 -21µ)48

“Baby” Grade Alpaca (22µ or less)

Mohair (23 – 28µ)

Superfine Merino (15.6 to 18.5µ)

Superfine Alpaca (26µ)

Standard Sheep’s Wool (30 – 32µ)

Human Hair (60 – 80µ)

Based on this criteria, these are the warmest woolens I could find:

Warmest Boot/Hiking Socks

90% Bison Wool Boot Socks by Buffalo Wool Company — highest percentage of bison wool in a boot sock — $54

Wayfarer Sock by Khunu — 56% yak wool, 34.5% nylon, 9.5% Elastane — £22 ($28 USD)

78% Alpaca Socks by Williamston Alpaca — 78% Alpaca, 20% Nylon, 2% Lycra — made in the USA — $22

Warmest Crew Socks

Warmest Indoor Socks

90% Yak Wool Socks by Yakamel — soft, inexpensive yak wool socks — $21

Bison and Silk Blend Socks by Fox River — these socks are great for indoor use — 36% bison wool, 36% silk, 26% nylon, 2% spandex — $43

90% Yak Wool Socks by DoctorTM — a bit thin but still warm — $13

Warmest Gloves

Warmest Hats

Warmest Scarves

Wool Fiber Reference