Decathlon to Gymshark leggings size

The short answer

Decathlon 2XS is Gymshark XXS by the two brands' own charts. 3 of 7 Decathlon sizes land on a different label at Gymshark.

Both brands publish the body waist each size is cut for, so every row matches a waist, not a tag.

Every Decathlon size read across to Gymshark. Letter sizes on the left, Letter on the right.
Decathlon	Decathlon builds it for	Gymshark, by chart	Same label	Gymshark builds it for	Gymshark also prints
2XS	waist 23.6 to 24.8 in, hip 31.1 to 33.5 in	XXS	XXS	waist 24 in, hip 35.5 in	US numeric 2-4
XS	waist 25.2 to 26.8 in, hip 33.5 to 35.4 in	XS	XS	waist 26 in, hip 37.5 in	US numeric 4-6
S	waist 27.2 to 28.7 in, hip 35.4 to 37.8 in	S	S	waist 28 in, hip 39.5 in	US numeric 6-8
M	waist 29.1 to 31.1 in, hip 37.8 to 40.2 in	M	M	waist 30 in, hip 41.5 in	US numeric 8-10
L	waist 31.5 to 33.9 in, hip 40.2 to 42.5 in	L or XL	L	waist 32 in, hip 43.5 in	US numeric 10-12
XL	waist 34.3 to 36.6 in, hip 42.5 to 44.9 in	XXL	XL	waist 36 in, hip 47.7 in	US numeric 14-16
2XL	waist 37 to 39.4 in, hip 44.9 to 47.2 in	XXL	XXL	waist 36 in, hip 47.7 in	US numeric 14-16

Tinted rows change label or sit between two sizes. Read from the two charts only; no formula and no averaging.

What wearers say

Charts describe a garment. People who own both brands describe a fit, and their answer ranks above this table once five of them stand behind it. Pick your size in the converter to see whether there are enough yet.

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Sources

Decathlon size guide, read on 2026-09-18.
Gymshark size guide, read on 2026-09-17. Gymshark on TrueToSize

Gymshark to Decathlon