Why this site exists
Most bra size calculators belong to companies that sell bras. That is not a crime, but it does mean every answer leads to a product page. KnowHerSize is independent. It has no stock to move, so it can focus on giving you the size and telling you how much to trust it.
It also has a second purpose. Plenty of people want to buy a gift for a partner and have no idea of her size. Most sites ignore them. This one gives them a clear, respectful route: find the size reliably if possible, and choose something forgiving if not.
How the sizing works
Every size on the site, in every chart, converter and calculator result, comes from one shared set of rules. Bands follow fixed conversions: US and UK use inches, Australia subtracts 22, Europe uses centimeters in 5 cm steps, and French sizing adds 15 to the European band. Cups go up one letter per inch of difference between bust and band, and each double letter counts as a full step.
Because there is one source of truth, the pages cannot disagree with each other. A US 34C is a UK 34C, an AU 12C, an EU 75C and a FR 90C everywhere on the site.
How we rate accuracy
The calculator offers four methods. Their reliability, from most to least, is:
- Measuring together.
- The tag on a bra that fits her well.
- An estimate from body shape.
- An estimate from clothing size.
Eyeballing sits below all four. Each result shows a confidence level that matches its method. Low-confidence results come with gift suggestions that do not depend on an exact size.
Where the facts come from
The guidance on this site draws on published fitting guides from lingerie retailers and specialist fitters, on fitting communities where many people compare their measurements and experiences, and on general lifestyle and men’s interest writing about buying lingerie as a gift. Where these sources disagree, we follow the method most fitting guides now use: a snug underbust for the band, with no inches added.
We do not invent statistics, studies or testimonials. If a page states a fact, it comes from that research or from the sizing rules above.
Editorial policy
- No brand pays for placement or wording on this site.
- Advertising is shown in clearly labeled slots and is kept out of the calculator steps.
- Any future affiliate links will be labeled and will not change results.
- Pages are reviewed when sizing guidance changes.
- Language stays respectful. Nobody’s body is a problem to be solved.
What the site will not do
It will not tell you that a size is certain when it is not. It will not shame anyone’s body or shape. And it will not push a product when a gift card would serve you better.
Privacy in one line
Your measurements are calculated in your browser and never sent or stored. The privacy policy has the details.
Contact
KnowHerSize is run by SIA „Vizo Media” in Latvia. Questions, corrections or a size that came out wrong: [email protected].
Sources & method: sizing rules follow the standard band-and-cup system used by UK, US, AU and EU brands, checked against fitting guides from specialist retailers and fitting communities. How we work.