Under Armour to lululemon clothing size

The short answer

Under Armour XXS is lululemon XS by the two brands' own charts. 7 of 8 Under Armour sizes land on a different label at lululemon.

Both brands publish the body bust each size is cut for, so every row matches a bust, not a letter or a number.

Every Under Armour size read across to lululemon. Letter sizes on the left, Letter on the right.
Under Armour	Under Armour builds it for	lululemon, by chart	Same label	lululemon builds it for	lululemon also prints
XXS	bust 31 to 32.5 in, waist 24.5 to 25.5 in	XS	XXS	bust 31 to 32 in	US 4
XS	bust 32.5 to 33.5 in, waist 25.5 to 27 in	S	XS	bust 33 to 34 in	US 6
SM	bust 33.5 to 36 in, waist 27 to 29 in	M	not published	bust 35 to 36 in	US 8
MD	bust 36 to 38 in, waist 29 to 31 in	L	not published	bust 37 to 38.5 in	US 10
LG	bust 38 to 41 in, waist 31 to 34 in	XL or L	not published	bust 40 to 42 in	US 12-14
XL	bust 41 to 44 in, waist 34 to 37 in	XL	XL	bust 40 to 42 in	US 12-14
XXL	bust 44 to 47 in, waist 37 to 40 in	1X	not published	bust 45 to 47 in	US 16-18
3XL	bust 47 to 50 in, waist 40 to 43 in	2X or 1X	not published	bust 49 to 51 in	US 20-22

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, 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.

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Sources

Under Armour size guide, read on 2026-09-18. Under Armour on TrueToSize
lululemon size guide, read on 2026-09-18. lululemon on TrueToSize

lululemon to Under Armour