Sizing: a medium is not the same sock
Darn Tough’s men’s/unisex medium covers US men’s 8 to 9.5; Smartwool’s medium covers 6 to 8.5 and its large 9 to 11.5. Darn Tough’s letters each span fewer shoe sizes, so check the chart for each brand rather than buying the same letter.
Heights: inches against names
Darn Tough publishes heel-to-cuff inches for every height (8.5 for a men’s micro crew, 10.5 for crew). Smartwool names its heights (ankle, low ankle, mid crew, crew) without inches. Compare cuffs against your shoe collar.
Cushion words
Darn Tough separates the knit weight (lightweight, midweight, heavyweight) from the cushion (no cushion, cushion, full cushion). Smartwool uses light, targeted, full, extra and maximum cushion. Neither is a shared scale.
Blend: check the exact pair
Both list merino with nylon and stretch fiber, and the share varies by model. Smartwool notes content can vary by UPC, so read the label on the pair you buy.
Guarantee: life against two years
Darn Tough promises to replace a pair for life; Smartwool offers a two-year satisfaction guarantee. Shop returns are separate and shorter. A longer guarantee is a promise, not a measured lifespan.
What this can’t tell you
This guide has not worn either brand. Which fits better depends on your foot and shoe; try the size each chart gives you and keep the pair unworn outside until you are sure.
