US: 3XL (46–48) to United Kingdom Size 38–40
Cross-market men’s underwear and boxer brief conversion mapping 3XL (46–48) specifications into 38–40.

Analyzing Underwear Size Equivalence Across Markets
US: 3XL (46–48): Corresponds to a waist stretch range of 116.8–121.9 (46–48 ), hip circumference of 127 (50 ), thigh clearance of 71 (28 ), and fit style Big & Tall Boxers & Briefs.
United Kingdom Size 38–40: Corresponds to a waist stretch range of 96.5–101.6 (38–40 ), hip circumference of 111.8 (44 ), thigh clearance of 63 (24.8 ), and fit style Relaxed Boxers & Extended Boxer Briefs.
Other Conversions to United Kingdom Size 38–40
US: XS (26–28) → uk-38-40XS (26–28) to uk-38-40
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US: S (28–30) → uk-38-40S (28–30) to uk-38-40
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US: M (31–33) → uk-38-40M (31–33) to uk-38-40
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US: L (34–36) → uk-38-40L (34–36) to uk-38-40
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US: XL (38–40) → uk-38-40XL (38–40) to uk-38-40
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US: 2XL (42–44) → uk-38-402XL (42–44) to uk-38-40
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US: 3XL (46–48) → uk-38-403XL (46–48) to uk-38-40
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