Reiss to Diane von Furstenberg clothing size

The short answer

Reiss 4 is Diane von Furstenberg XXS 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 Reiss size read across to Diane von Furstenberg. UK sizes on the left, Letter on the right.
Reiss	Reiss builds it for	Diane von Furstenberg, by chart	Same label	Diane von Furstenberg builds it for	Diane von Furstenberg also prints
4	bust 31 in, waist 24 in, hip 34 in	XXS	XS	bust 31 in, waist 24 in, hip 34 in	US 00
6	bust 32 in, waist 25 in, hip 35 in	XS	XS	bust 32 in, waist 25 in, hip 35 in	US 0
8	bust 33 in, waist 26 in, hip 36 in	S	S	bust 33 to 34 in, waist 26 to 27 in, hip 36 to 37 in	US 2/4
10	bust 35 in, waist 28 in, hip 38 in	M	S	bust 35 to 36 in, waist 28 to 29 in, hip 38 to 39 in	US 6/8
12	bust 37 in, waist 30 in, hip 40 in	L	M	bust 37 to 38.5 in, waist 30 to 31.5 in, hip 40 to 41.5 in	US 10/12
14	bust 39 in, waist 31.5 in, hip 42 in	L or XL	M	bust 37 to 38.5 in, waist 30 to 31.5 in, hip 40 to 41.5 in	US 10/12
16	bust 41 in, waist 33.5 in, hip 44 in	XL	L	bust 40 to 42 in, waist 33 to 35 in, hip 43 to 45 in	US 14/16
18	bust 43 in, waist 36 in, hip 46.5 in	XL	L	bust 40 to 42 in, waist 33 to 35 in, hip 43 to 45 in	US 14/16

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

Reiss size guide, read on 2026-09-18.
Diane von Furstenberg size guide, read on 2026-09-18.

Diane von Furstenberg to Reiss