Smartwool to Aerie (OFFLINE) leggings size

The short answer

Smartwool S is Aerie (OFFLINE) M or L by the two brands' own charts. 4 of 4 Smartwool sizes land on a different label at Aerie (OFFLINE).

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

Every Smartwool size read across to Aerie (OFFLINE). Letter sizes on the left, Letter on the right.
Smartwool	Smartwool builds it for	Aerie (OFFLINE), by chart	Same label	Aerie (OFFLINE) builds it for	Aerie (OFFLINE) also prints
S	waist 29 to 31 in, hip 36 to 38 in	M or L	S	waist 28.5 to 29.5 in, hip 38 to 39 in	US numeric 8-10
M	waist 32 to 34 in, hip 39 to 41 in	L or XL	M	waist 31 to 32.5 in, hip 40.5 to 42 in	US numeric 12-14
L	waist 35 to 37 in, hip 42 to 44 in	XL	L	waist 34 to 36 in, hip 43.5 to 45.5 in	US numeric 16-18
XL	waist 38 to 40 in, hip 45 to 48 in	XXL	XL	waist 38 in, hip 47.5 in	US numeric 20
XXL	waist 41 to 44 in, hip 49 to 51 in	not made	XXL	not published	not published

Tinted rows change label or sit between two sizes. 1 sizes have no counterpart on the Aerie (OFFLINE) chart. 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

Smartwool size guide, read on 2026-09-18.
Aerie (OFFLINE) size guide, read on 2026-09-18. Aerie (OFFLINE) on TrueToSize

Aerie (OFFLINE) to Smartwool