TrueToSize

Convert / Women's clothing

Gap to Reformation clothing size

The short answer

Gap 18 is Reformation 1X or XL 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 Gap size read across to Reformation. US sizes on the left, Letter on the right.
GapGap builds it forReformation, by chartSame labelReformation builds it forReformation also prints
000bust 30.3 in, waist 24 in, hip 33.3 innot madenot publishednot publishednot published
000bust 30.3 in, waist 24 in, hip 33.3 innot madenot publishednot publishednot published
000bust 30.3 in, waist 24 in, hip 33.3 innot madenot publishednot publishednot published
2bust 33.3 in, waist 26.5 in, hip 36.3 inXSXSbust 33 in, waist 25 in, hip 36 inUS 0
4bust 34.3 in, waist 27.5 in, hip 37.3 inS or XSSbust 35 in, waist 27 in, hip 38 inUS 2/4
6bust 35.3 in, waist 28.5 in, hip 38.3 inSSbust 35 in, waist 27 in, hip 38 inUS 2/4
8bust 36.3 in, waist 29.5 in, hip 39.3 inM or SMbust 37 in, waist 29 in, hip 40 inUS 6/8
10bust 37.3 in, waist 30.5 in, hip 40.3 inMMbust 37 in, waist 29 in, hip 40 inUS 6/8
12bust 38.8 in, waist 32 in, hip 41.8 inLLbust 39.5 in, waist 31.5 in, hip 42.5 inUS 10
14bust 40.3 in, waist 33.5 in, hip 43.3 inL or XLLbust 39.5 in, waist 31.5 in, hip 42.5 inUS 10
16bust 42 in, waist 35.5 in, hip 45.3 inXLXLbust 41.5 in, waist 33.5 in, hip 44.5 inUS 12
18bust 43.8 in, waist 37.5 in, hip 47.3 in1X or XLXLbust 45 in, waist 37.5 in, hip 47.5 inUS 14
20bust 45.8 in, waist 39.5 in, hip 49.3 in1Xnot publishedbust 45 in, waist 37.5 in, hip 47.5 inUS 14
22bust 47.8 in, waist 41.5 in, hip 51.3 in2Xnot publishedbust 48 in, waist 40.5 in, hip 50.5 inUS 16/18
Tinted rows change label or sit between two sizes. 3 sizes have no counterpart on the Reformation 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

Reformation to Gap