Boden to Reformation clothing size

The short answer

Boden 4 is Reformation XS 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 Boden size read across to Reformation. US sizes on the left, Letter on the right.
Boden	Boden builds it for	Reformation, by chart	Same label	Reformation builds it for	Reformation also prints
2	bust 32 to 33 in, waist 25 to 26 in, hip 34 to 35 in	XS	XS	bust 33 in, waist 25 in, hip 36 in	US 0
4	bust 33.3 to 34 in, waist 26.3 to 27 in, hip 35.3 to 36 in	XS	S	bust 33 in, waist 25 in, hip 36 in	US 0
6	bust 34.3 to 35 in, waist 27.3 to 28 in, hip 36.3 to 37 in	S	S	bust 35 in, waist 27 in, hip 38 in	US 2/4
8	bust 35.5 to 37 in, waist 28.5 to 30 in, hip 37.5 to 39 in	M or S	M	bust 37 in, waist 29 in, hip 40 in	US 6/8
10	bust 37.5 to 39 in, waist 30.5 to 32 in, hip 39.5 to 41 in	M or L	M	bust 37 in, waist 29 in, hip 40 in	US 6/8
12	bust 39.5 to 41 in, waist 32.5 to 34 in, hip 41.5 to 43 in	L or XL	L	bust 39.5 in, waist 31.5 in, hip 42.5 in	US 10
14	bust 41.5 to 43 in, waist 34.5 to 36 in, hip 43.5 to 45 in	XL	L	bust 41.5 in, waist 33.5 in, hip 44.5 in	US 12
16	bust 43.5 to 45 in, waist 36.5 to 38 in, hip 45.5 to 47 in	1X	XL	bust 45 in, waist 37.5 in, hip 47.5 in	US 14
18	bust 45.5 to 47.5 in, waist 38.5 to 40.5 in, hip 47.5 to 49.5 in	1X or 2X	XL	bust 45 in, waist 37.5 in, hip 47.5 in	US 14

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

Boden size guide, read on 2026-09-18.
Reformation size guide, read on 2026-09-18. Reformation on TrueToSize

Reformation to Boden