Harper Wilde to ThirdLove bra size

The short answer

Harper Wilde 34DD is ThirdLove 34E by the two brands' own charts. 2 of 6 Harper Wilde sizes land on a different label at ThirdLove.

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

Every Harper Wilde size read across to ThirdLove. US sizes on the left, US on the right.
Harper Wilde	Harper Wilde builds it for	ThirdLove, by chart	Same label	ThirdLove builds it for	ThirdLove also prints
34A	not published	34A	not published	not published	not published
34B	not published	34B	not published	not published	not published
34C	not published	34C	not published	not published	not published
34D	not published	34D	not published	not published	not published
34DD	not published	34E	not published	not published	not published
34DDD	not published	34F	not published	not published	not published

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

Harper Wilde size guide, read on 2026-09-18. Harper Wilde on TrueToSize
ThirdLove size guide, read on 2026-09-17. ThirdLove on TrueToSize

ThirdLove to Harper Wilde