ThirdLove bra size chart, converted to UK and US sizes
ThirdLove sizes in US letters with half cups of its own (32B½, for example), and its calculator put the band 2 to 3 in above the underbust in all five runs that returned a size. Read from ThirdLove's chart page, measuring guide and calculator on 25 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 five successful calculator runs put the band 2 to 3 in above the underbust. We could not reproduce its cup rule. White and Scurr (2012) studied the traditional +4 method, not ThirdLove's calculator. Check the fit rather than assuming either label will work at another brand.
We quote its chart-page text, measuring guide and recorded calculator answers 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 chart page states a range of AA to H, plus half cups. The table below covers AA to DDD on bands 32 to 38 using our US-to-UK ladder; it is not a list of available bras. ThirdLove's guide confirms DD = E and DDD = F, but we could not read its image chart as text to verify every pairing. Its guide says not to round measurements to a whole number and to try a half cup between sizes. At another brand, our advice is to try the full letters above and below.
| 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. For bands 40 to 44 or G and H cups, check ThirdLove's own chart before using the generic six-system 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; 6 synthetic pairs submitted to the calculator; 5 result pairs recorded (opened 25 September 2026)
- ThirdLove, "How To Measure Your Bra Size At Home": DD = E and DDD = F; half-cup sizes; do not round (opened 25 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