Bras N Things to Harper Wilde bra size

The short answer

Bras N Things 12D is Harper Wilde 34D by the two brands' own charts.

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

Every Bras N Things size read across to Harper Wilde. AU sizes on the left, US on the right.
Bras N Things	Harper Wilde, by chart	Same label	Harper Wilde also prints
12A	34A	not published	not published
12B	34B	not published	not published
12C	34C	not published	not published
12D	34D	not published	not published
12DD	34DD	not published	not published
12E	34DDD	not published	not published
12F	not made	not published	not published
12G	not made	not published	not published

Neither chart publishes the body each size is built for, so the rows line up the labels. Tinted rows change label or sit between two sizes. 2 sizes have no counterpart on the Harper Wilde chart. 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

Bras N Things size guide, read on 2026-09-18.
Harper Wilde size guide, read on 2026-09-18. Harper Wilde on TrueToSize

Harper Wilde to Bras N Things