About Brasize.ai
A precision measurement tool for bra sizing. Not a lingerie brand, not a store: a place to get an exact size and understand why it's right.
Sizing intelligence, not shopping
Most bra size calculators exist to sell you a bra. Many still use a decades-old formula that adds four inches to your band, because it happens to steer people toward the sizes a store stocks. The result is the statistic everyone has heard: a large majority of women wear the wrong size, usually a band too loose and a cup too small.
Brasize.ai was built to be the reference instead of the shop. We use the modern snug-measure method professional fitters use, we show the calculation rather than hiding it, and we give you the surrounding system: sister sizes, eight international conversions, and fit diagnostics, so the answer makes sense.
Nothing to sign up for. Nothing stored. Measurements are calculated in your browser and never leave it.
How we work
Every result on Brasize.ai can be traced to two measurements and one subtraction. If you can't see how a number was reached, you can't trust it.
Sizes are a starting point. We pair every result with sister sizes and fit checks because the label is only right when the bra is.
This site doesn't sell bras, and no brand pays for placement or ranking here. Full transparency: brasize.ai's owner also owns the lingerie retailer HauteFlair. Because of that, HauteFlair is held to the same rules as every other retailer on this site: listed alphabetically, described in the same neutral terms, and audited to the identical standard in our brand-chart research. Where we mention any brand or retailer, it's to explain how their sizing works, not to sell them.
How the calculator works
The underbust reading is rounded to the nearest even inch. Nothing is added. Odd readings round up, and the result page shows the sister size on the band below so you can let the band decide.
The bust reading at the fullest point minus the band, one letter per inch, on the US scale AA–K. The same difference is then written in UK and EU letters where they diverge above D.
Sister sizes (band ∓2, cup ±1), eight-system conversions (published band formulas), and the +4-method twin (band −4, cup +2) are all computed from those two numbers. There is no lookup table to be wrong.
Full formulas and conventions are documented in the editorial policy.
Built by NativeCode
Brasize.ai is a project of NativeCode, a product studio building reference-grade tools for questions people ask every day. Our sizing methodology is published in full, our review process is described on the fit team page, and journalists will find checked figures on Bra sizing by the numbers.
Questions, corrections, or a brand's sizing convention we've got wrong? Get in touch: accuracy reports are the most useful mail we get.
Opens HauteFlair’s own hub page; use your measured size there. HauteFlair is owned by the same company as Brasize.ai; that relationship never changes the sizing math, charts, or fit advice on this page. How this site makes money.
Full detail on shop links and commissions: the affiliate disclosure.