Reiss to Farm Rio clothing size

The short answer

Reiss 4 is Farm Rio 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 Farm Rio. UK sizes on the left, Letter on the right.
Reiss	Reiss builds it for	Farm Rio, by chart	Same label	Farm Rio builds it for	Farm Rio also prints
4	bust 31 in, waist 24 in, hip 34 in	XXS	XS	bust 30 to 31 in, waist 24 to 25 in, hip 33 to 34 in	US 00 · UK 2 · EU (as printed) 30
6	bust 32 in, waist 25 in, hip 35 in	XS	XS	bust 32 to 33 in, waist 26 to 27 in, hip 35 to 36 in	US 0-2 · UK 4-6 · EU (as printed) 32-34
8	bust 33 in, waist 26 in, hip 36 in	XS	S	bust 32 to 33 in, waist 26 to 27 in, hip 35 to 36 in	US 0-2 · UK 4-6 · EU (as printed) 32-34
10	bust 35 in, waist 28 in, hip 38 in	S	S	bust 34 to 35 in, waist 28 to 29 in, hip 37 to 38 in	US 4-6 · UK 8-10 · EU (as printed) 36-38
12	bust 37 in, waist 30 in, hip 40 in	M	M	bust 36 to 37 in, waist 30 to 31 in, hip 39 to 40 in	US 8-10 · UK 12-14 · EU (as printed) 40-42
14	bust 39 in, waist 31.5 in, hip 42 in	L	M	bust 38 to 40 in, waist 32 to 34 in, hip 41 to 43 in	US 12-14 · UK 16-18 · EU (as printed) 44-46
16	bust 41 in, waist 33.5 in, hip 44 in	XL	L	bust 41 to 44 in, waist 35 to 37 in, hip 44 to 46 in	US 16 · UK 20 · EU (as printed) 48
18	bust 43 in, waist 36 in, hip 46.5 in	XL	L	bust 41 to 44 in, waist 35 to 37 in, hip 44 to 46 in	US 16 · UK 20 · EU (as printed) 48

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.
Farm Rio size guide, read on 2026-09-18.

Farm Rio to Reiss