MUJI to Gap clothing size

The short answer

MUJI L is Gap 4 or 6 by the two brands' own charts.

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

Every MUJI Japan sizing size read across to Gap. Letter sizes on the left, US on the right.
MUJI Japan sizing	MUJI builds it for	Gap, by chart	Same label	Gap builds it for	Gap also prints
XS	bust 28.7 to 30.3 in, waist 22.1 to 23.6 in, hip 31.9 to 33.5 in	000	not published	bust 30.3 in, waist 24 in, hip 33.3 in	Letter XXS
S	bust 29.5 to 31.9 in, waist 22.8 to 25.2 in, hip 32.7 to 35 in	000 or 00	not published	bust 30.3 in, waist 24 in, hip 33.3 in	Letter XXS
M	bust 31.5 to 33.9 in, waist 24.8 to 27.2 in, hip 34.7 to 37 in	0 or 2	not published	bust 32.3 in, waist 25.5 in, hip 35.3 in	Letter XS
L	bust 33.5 to 35.8 in, waist 26.8 to 29.1 in, hip 36.6 to 39 in	4 or 6	not published	bust 34.3 in, waist 27.5 in, hip 37.3 in	Letter S
XL	bust 35.4 to 37.8 in, waist 28.7 to 31.1 in, hip 38.6 to 40.9 in	8 or 10	not published	bust 36.3 in, waist 29.5 in, hip 39.3 in	Letter M
XXL	bust 37.4 to 39.8 in, waist 30.7 to 33.1 in, hip 40.6 to 42.9 in	12	not published	bust 38.8 in, waist 32 in, hip 41.8 in	Letter L

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

MUJI Japan sizing size guide, read on 2026-09-25.
Gap size guide, read on 2026-09-18. Gap on TrueToSize

Gap to MUJI