Bra AtlasBra sizing, measured and sourced

About Bra Atlas

A bra sizing reference built on one engine. The calculator, reference charts and size pages share its size, conversion and sister-size rules. Brand charts are separate evidence: where their labels differ from the reference, the page explains the difference.

Who makes it

Bra Atlas is built and maintained by Rai Ansar, a software developer. It grew out of a sizing draft supplied by a content partner; the calculators were rebuilt around one shared engine.

This is a sizing reference, not a fitting service. Fit advice links to research or brand fitting guides so you can check the source. Contact: hello@braatlas.com.

How pages are made

  • The engine. One TypeScript module computes every size on the site: the measured-band method, the traditional +4 method, the six label systems and sister sizes. The full method is on the calculator page.
  • The tests. On 25 September 2026, 18 synthetic measurement pairs were entered into A Bra That Fits and 10 pairs into calculator.net. Tests compare our UK, US, EU, French and Australian labels with the recorded A Bra That Fits results; Japan remains approximate. In those fixtures, all three underbust readings were equal and all three bust readings were equal. This does not make our two-input method identical to its six-input method. The A Bra That Fits fixtures and calculator.net output labels are available to read.
  • Brand charts. On 25 September 2026 we opened Victoria's Secret, ThirdLove, Wacoal, SKIMS, Marks & Spencer and Freya size pages in a browser, saved their text, and typed six to eight tape measurements into the Wacoal and ThirdLove calculators. Tests check the brand page against those captures; where a brand's chart disagrees with ours (Freya's Australian letters), the page says so.
  • Sources. Every outside fact links to where it came from, with the date it was checked. Where sources disagree (Japanese and Australian cup letters, EU cups), the page says so.
  • Dates. The "checked" date changes only when sources are re-opened or numbers change.

Money

There are no ads on the site. As an Amazon Associate I earn from qualifying purchases. Size pages carry Amazon Associates search links ("Shop [size] bras on Amazon"), added 26 September 2026 once the Amazon Global Earning tracking id was created. Every link is labeled as an affiliate link next to it, opens a plain amazon.com search for that size (not a specific product we picked), and never changes the size the calculator shows. The Bravissimo, Wacoal, ThirdLove and Marks & Spencer slots described in our code are still unjoined; if one of those goes live, this page and the privacy page will be updated first.

Sources

Each source was opened and checked on 25 September 2026. Where sources disagree, the page says so instead of picking one silently.

  1. A Bra That Fits calculator (community calculator of r/ABraThatFits): we submitted 18 measurement pairs in 6 systems on 25 September 2026; raw synthetic fixture outputs are linked from the methodology
  2. calculator.net, Bra Size Calculator: 10 measurement pairs run in a browser on 25 September 2026
  3. Wikipedia, "Bra size": UK and US cup ladders, the +4 method, EN 13402 and JIS cup steps
  4. 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