Sandro to Gap clothing size

The short answer

Sandro 34 is Gap 0 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 Sandro size read across to Gap. FR sizes on the left, US on the right.
Sandro	Sandro builds it for	Gap, by chart	Same label	Gap builds it for	Gap also prints
34	bust 32 in, waist 25 in, hip 35 in	0	2	bust 32.3 in, waist 25.5 in, hip 35.3 in	Letter XS
36	bust 34 in, waist 27 in, hip 36 in	4	4	bust 34.3 in, waist 27.5 in, hip 37.3 in	Letter S
38	bust 35 in, waist 28 in, hip 38 in	6	6	bust 35.3 in, waist 28.5 in, hip 38.3 in	Letter S
40	bust 37 in, waist 30 in, hip 39 in	10	8	bust 37.3 in, waist 30.5 in, hip 40.3 in	Letter M
42	bust 39 in, waist 31 in, hip 41 in	12	10	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

Sandro size guide, read on 2026-09-18.
Gap size guide, read on 2026-09-18. Gap on TrueToSize

Gap to Sandro