US: 54-56 to United Kingdom Size 34-36
Cross-market men’s sleepwear conversion mapping 54-56 specifications into 34-36 for lounge pants, pajama sets, and robes.

Analyzing Sleepwear Size Equivalence Across Markets
US: 54-56: Corresponds to a relaxed chest range of 130–134 (51.2–52.8 ), elastic waist range of 116–122 (45.7–48 ), and fit classification Loose Lounge Fit.
United Kingdom Size 34-36: Corresponds to a relaxed chest range of 90–94 (35.4–37 ), elastic waist range of 76–82 (29.9–32.3 ), and fit classification Relaxed / Comfort Fit.