US: 13.5–15 to United Kingdom Size 15–17.5
Cross-market men’s sock conversion mapping 13.5–15 specifications into 15–17.5.

Analyzing Sock Size Equivalence Across Markets
US: 13.5–15: Corresponds to a US shoe size range of 13.5–15, foot length of 30.5–32 (12–12.6 ), and fit classification Extended Volume / High Stretch.
United Kingdom Size 15–17.5: Corresponds to a US shoe size range of 15.5–18, foot length of 32.5–35 (12.8–13.8 ), and fit classification Max Volume / Bariatric & Therapeutic.