GU to Gymshark size
The short answer
GU M is Gymshark XS by the two brands' own charts. 5 of 5 GU sizes land on a different label at Gymshark.
Both brands publish the body chest each size is cut for, so every row matches a chest, not a letter.
On 2 sizes the charts land two or more sizes from the same label. Brands do not measure the body the same way, so on those rows treat the chart answer and the same label as the two ends of a range.
| GU Japan sizing | GU builds it for | Gymshark, by chart | Same label | Gymshark builds it for | Gymshark also prints |
|---|---|---|---|---|---|
| XS | chest 29.9 to 33.1 in, waist 25.2 to 28.4 in | not made | XS | not published | not published |
| S | chest 31.5 to 34.7 in, waist 26.8 to 29.9 in | not made | S | not published | not published |
| M | chest 34.7 to 37.8 in, waist 29.9 to 33.1 in | XS | M | chest 37 in, waist 29.5 in | not published |
| L | chest 37.8 to 40.9 in, waist 33.1 to 36.2 in | S | L | chest 39 in, waist 31.5 in | not published |
| XL | chest 40.9 to 44.1 in, waist 36.2 to 39.4 in | L | XL | chest 43 in, waist 35.5 in | not published |
| XXL | chest 44.1 to 47.2 in, waist 39.4 to 42.5 in | XL | XXL | chest 45 in, waist 37.5 in | not published |
| 3XL | chest 47.2 to 50.4 in, waist 42.5 to 45.7 in | XXXL | XXXL | chest 49 in, waist 41.5 in | not published |
What wearers say
Charts describe a garment, not a fit. We do not collect fit reports for this category yet, so this table is the two brands' own claims and nothing more.
Sources
- GU Japan sizing size guide, read on 2026-09-25.
- Gymshark size guide, read on 2026-09-18. Gymshark on TrueToSize