ThirdLove bra size chart, converted to UK and US sizes
"thirdlove bra size chart" gets 2,400 US searches a month. ThirdLove sizes in US letters with half cups of its own (32B½, for example), and its calculator padded the band in every one of our test runs. Read from ThirdLove's own chart and calculator on 26 September 2026.
Same tape, three answers
| Method | Result |
|---|---|
| Bra Atlas (measured band) | 34D |
| ThirdLove's calculator | 36A |
| Wacoal's calculator | 36B (see the Wacoal page) |
ThirdLove's 36A holds less cup volume than our 34D: its calculator pads the band by 2 to 3 in before it reads a cup off the tape, the same padded-band pattern White and Scurr (2012) measured against professional fitting. Neither answer is "wrong" for ThirdLove's own bras; it just means a ThirdLove size does not carry over to another brand.
ThirdLove did not pay for a mention. We quote what its chart and calculator printed and say where that differs from a measured-band size; we don't claim ThirdLove "runs small".
What ThirdLove's own chart and guide say
From thirdlove.com's bra size chart page and its "How To Measure" guide.
What its calculator printed
We gave its bra size calculator six tape measurements. 30/34 in came back 32B½, 32/35 came back 34AA, 33/37 came back 36A, 34/38 came back 36A and 36/41 came back 38A; 38/44 returned "we don't currently carry your size". Our measured-band engine gives 30D, 32C, 34C/D, 34D, 36DD and 38E for the same pairs.
Its letters
ThirdLove's own measuring guide says a DD is the same as an E and a DDD is the same as an F. Its half cups sit between two letters, so a 34C½ has no exact label at another brand: try the letter above and below.
Reading it
The padded band is the older +4 idea in a milder form (+2 or +3). Its cups did not follow one subtraction rule we could reproduce from six pairs, so we publish what it printed and nothing more.
Converting a ThirdLove size
ThirdLove's full-letter sizes (AA to DDD) use the same US cup letters our engine does, so a ThirdLove label converts the same way any US size does. Its half-cup sizes (a 32B½, for example) sit between two of these letters; ThirdLove's own guide says try the letter above and below rather than rounding.
| Band | AA | A | B | C | D | DD | DDD |
|---|---|---|---|---|---|---|---|
| 32 | 32AA | 32A | 32B | 32C | 32D | 32DD | 32E |
| 34 | 34AA | 34A | 34B | 34C | 34D | 34DD | 34E |
| 36 | 36AA | 36A | 36B | 36C | 36D | 36DD | 36E |
| 38 | 38AA | 38A | 38B | 38C | 38D | 38DD | 38E |
Built from the same conversion engine as the rest of the site (src/lib/engine.ts); nothing here is typed by hand. A ThirdLove 34DDD, for example, reads 34E on our chart, EU 75F and France 90F. Full six-system conversions, including EU, France, Australia and Japan, are on the converter.
Sources
Each source was opened and checked on the date shown, or on 25 September 2026. Where sources disagree, the page says so instead of picking one silently.
- ThirdLove, "Bra Size Calculator & Chart": bands 32 to 44, cups AA to H with half cups; calculator run with 6 measurement pairs (opened 26 September 2026)
- ThirdLove, "How To Measure Your Bra Size At Home": DD = E and DDD = F; half-cup sizes; do not round (opened 26 September 2026)
- White J, Scurr J. Evaluation of professional bra fitting criteria for bra selection and fitting in the UK. Ergonomics 2012;55(6):704-711: 45 women; the traditional method overestimated band and underestimated cup