One thin-to-medium pair. This is the one place on the site where the intuitive answer is reliably wrong, and it is wrong for a physical reason rather than a matter of taste.
Why two pairs are colder
Insulation is trapped still air. A ski boot is a fixed volume; put two pairs of socks into it and the fill in both is compressed, and compressed material holds almost no air.
Worse, the extra bulk squeezes the foot. Restricted circulation is the main cause of cold feet in a boot that otherwise fits, and it is a self-inflicted one.
Why thick is not warm either
The same argument in one pair. A very thick sock in a fitted boot compresses, and it also changes the fit — a boot shell-fitted with a thin sock is loose with a thick one and then tightened with the buckles, which returns to the squeezing problem.
What a ski sock should be
Merino or a high merino blend. Wool holds warmth when damp, resists smell over several days, and does not go clammy the way cotton does. The percentage matters more than the word: “merino blend” covers everything from most of the sock to a token amount.
Padding in the right places only. Shin, instep and heel — where the shell presses. Padding across the sole is padding in the way.
Long enough to clear the cuff, which is why they are sold knee length.
No cotton, at all.
The other habits
Put the sock on smooth, with no wrinkle at the instep — that is the origin of most first-day pain blamed on the boot. Fresh pair every day or two. Dry the liners overnight, which does more for warm feet than any sock.
How this site prints it
Sock pages print the merino content where the maker states it, the thickness, where the padding sits, the height and the size bracket. They also print the pack count and the price per pair, because this shelf is sold in twos and threes at prices that only compare that way.
The questions asked most often
My feet are cold in one pair. Surely two is warmer?
Not inside a fitted boot. The second pair compresses the first, removes the air that was insulating and squeezes the foot, and restricted circulation is what makes feet cold.
Do ski socks really need to be knee length?
They need to clear the boot cuff. A sock that stops below the shell puts a seam exactly where the plastic presses, which is where the bruise comes from.
Last reviewed 28 September 2026