Whistles to Sandro clothing size

The short answer

Whistles 12 is Sandro 38 or 40 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 Whistles size read across to Sandro. UK sizes on the left, FR on the right.
Whistles	Whistles builds it for	Sandro, by chart	Same label	Sandro builds it for	Sandro also prints
04	bust 30 in, waist 23.5 in, hip 34.5 in	not made	not published	not published	not published
06	bust 31 in, waist 24.5 in, hip 35.5 in	34	not published	bust 32 in, waist 25 in, hip 35 in	US 2 · Letter XS · UK 6 · DE 32 · IT 38
08	bust 32 in, waist 25.5 in, hip 36.5 in	34	not published	bust 32 in, waist 25 in, hip 35 in	US 2 · Letter XS · UK 6 · DE 32 · IT 38
10	bust 34 in, waist 27.5 in, hip 38.5 in	36	not published	bust 34 in, waist 27 in, hip 36 in	US 4 · Letter S · UK 8 · DE 34 · IT 40
12	bust 36 in, waist 29.5 in, hip 40.5 in	38 or 40	not published	bust 35 in, waist 28 in, hip 38 in	US 6 · Letter M · UK 10 · DE 36 · IT 42
14	bust 38 in, waist 31.5 in, hip 42.5 in	40 or 42	not published	bust 37 in, waist 30 in, hip 39 in	US 8 · Letter L · UK 12 · DE 38 · IT 44
16	bust 40 in, waist 33.5 in, hip 44.5 in	42	not published	bust 39 in, waist 31 in, hip 41 in	US 10 · Letter XL · UK 14 · DE 40 · IT 46
18	bust 42.5 in, waist 35.5 in, hip 46.5 in	not made	not published	not published	not published
20	bust 45 in, waist 38 in, hip 49 in	not made	not published	not published	not published

Tinted rows change label or sit between two sizes. 3 sizes have no counterpart on the Sandro chart. 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

Whistles size guide, read on 2026-09-18.
Sandro size guide, read on 2026-09-18.

Sandro to Whistles