US: 20-22 to United Kingdom Size 4-6
Cross-market women’s sleepwear conversion mapping 20-22 specifications into 4-6 for nightgowns, pajama sets, and sleep shirts.

Analyzing Women’s Sleepwear Equivalence Across Markets
US: 20-22: Corresponds to a relaxed bust range of 113–117 (44.5–46.1 ), elastic waist range of 95–100 (37.4–39.4 ), and comfort drape classification Loose Lounge Fit.
United Kingdom Size 4-6: Corresponds to a relaxed bust range of 78–82 (30.7–32.3 ), elastic waist range of 60–64 (23.6–25.2 ), and comfort drape classification Relaxed / Comfort Drape.