True & Co to Bras N Things bra size

The short answer

True & Co XL is Bras N Things 18C by the two brands' own charts.

Cups are counted along each brand's own letter order, and the band is carried across unchanged.

Every True & Co size read across to Bras N Things. Brand's own sizes on the left, AU on the right.
True & Co	True & Co builds it for	Bras N Things, by chart	Same label	Bras N Things builds it for	Bras N Things also prints
XS	not published	10C	not published	not published	UK C · US C · EU C · FR C
S	not published	12C	not published	not published	UK C · US C · EU C · FR C
M	not published	14C	not published	not published	UK C · US C · EU C · FR C
L	not published	16C	not published	not published	UK C · US C · EU C · FR C
XL	not published	18C	not published	not published	UK C · US C · EU C · FR C
1X	not published	20C	not published	not published	UK C · US C · EU C · FR C
2X	not published	22C	not published	not published	UK C · US C · EU C · FR C
3X	not published	24C	not published	not published	UK C · US C · EU C · FR C

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. People who own both brands describe a fit, and their answer ranks above this table once five of them stand behind it. Pick your size in the converter to see whether there are enough yet.

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Sources

True & Co size guide, read on 2026-09-18. True & Co on TrueToSize
Bras N Things size guide, read on 2026-09-18.

Bras N Things to True & Co