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Measured on six things
Free on-device bra size calculator: inches or cm, US/UK/EU/FR/AU labels, sister sizes, fit journal—no account.
Security
52HTTPS with HSTS, X-Content-Type-Options and Referrer-Policy set, and local-only processing is a real privacy win. But no CSP, no frame protection, no SPF/DMARC, and no published security or privacy detail beyond a one-line claim.
Screenshots
1 / 1
About this app
Bra Size Calculator turns underbust and bust measurements into a starting band and cup size. Supports quick or six-measurement modes, sister sizes, US/UK/EU/FR/AU conversions, and an optional try-on journal. Measurements stay on your device. A size to try—not a guarantee of fit. Finding a bra that actually fits shouldn't feel like a guessing game. This free browser-based tool offers three modes: a quick two-measurement estimate, a six-measurement method, and an "I know my size" converter for translating an existing label. It compares US, UK, EU, France/Spain/Belgium, and Australia/NZ labels, and suggests sister sizes when the cups fit but the band doesn't. The illustrated measuring guide walks you through each step, and a built-in try-on journal lets you save bras you've tried. Everything runs locally: no account, no photos, no measurements sent anywhere.
Key features
- 1Three modes: quick two-measurement estimate, six-measurement method, and existing-label converter.
- 2Cross-brand conversion across US, UK, EU, France/Spain/Belgium, and Australia/NZ sizing systems.
- 3Sister-size suggestions and a fit checker for band/cup issues, plus a local try-on journal.
- 4Free, no sign-up, measurements processed locally with no uploads or account.
Target customer profile
Drawn from the product itself, not from a survey.
Demographic
Women who've never been professionally fitted (late teens to 30s)
Pain points
Guessing sizes online leads to constant returns and bras that dig, ride up, or gap
Primary needs
Clear step-by-step measuring guidance and a reliable starting label to shop with
Demographic
Frequent online bra shoppers across multiple brands
Pain points
Labels differ between US, UK, and EU brands, making cross-brand sizing confusing
Primary needs
Quick international size conversion and sister-size suggestions before checkout
Demographic
People whose body size or shape has recently changed
Pain points
Old bras no longer fit but they're unsure how to re-measure at home
Primary needs
A private, no-sign-up six-measurement method and a way to log which sizes worked
Demographic
Budget-conscious shoppers who avoid boutique fittings
Pain points
In-store fittings feel intimidating or pushy; paid apps add another cost
Primary needs
A genuinely free tool with no account, no upsells, and full data privacy
Scout Review
Written by AI from measured evidence, scored out of 100.
Bra Size Calculator is a focused, genuinely useful free tool that solves a real and annoying problem: translating measurements and labels across five sizing systems without an account or a pushy fitting. The execution is competent — fast, accessible on automated checks, and designed with a calm, trustworthy tone. It falls short on the details: keyword-stuffed copy, a clipped size chart, buried guidance, thin security headers, and no published privacy or accessibility documentation. Against its peers it holds its own on neutrality and privacy, and loses on depth of documentation and brand trust. A strong starting point that needs polish and a clearer trust story.
Measure by measure
Usability
62Three clear modes, in/cm toggle, country selector and a visible example path make the core flow obvious. Guidance buried in disclosure triangles and a dense lower half slow first-timers down.
Design
58Calm monochrome palette with one blue accent and disciplined monospace eyebrow labels give it a clinical, trustworthy feel. Undercut by keyword-stuffed copy, a clipped size chart, and tiny grey footnotes.
Speed
88Lighthouse 100/100 on both mobile and desktop, LCP 928ms, zero CLS and zero TBT. Genuinely fast, static-feeling page with no bloat in the critical path.
Security
52HTTPS with HSTS, X-Content-Type-Options and Referrer-Policy set, and local-only processing is a real privacy win. But no CSP, no frame protection, no SPF/DMARC, and no published security or privacy detail beyond a one-line claim.
Accessibility
78Lighthouse a11y 100/100 with one failing audit on mismatched accessible names. No WCAG statement or a11y page published, and the UI is English-only despite five sizing systems.
Growth
58Real, specific problem (cross-brand label chaos) with a genuine wedge: free, neutral, no sign-up, local-only, plus a try-on journal. Early domain, but the idea has a clear reason to exist.
Improvement areas
- Keyword-heavy repetitive copy weakens readability and reads as SEO filler.
- International size chart clipped at the bottom with an inner scrollbar.
- No published privacy policy, security page, or accessibility statement.
- Missing CSP, frame protection, Permissions-Policy, SPF and DMARC headers.
Design & Usability
The design reads as deliberate: a restrained monochrome palette, one blue accent, and a consistent monospace labeling system ('01 / ENTER YOUR DETAILS') that makes a sensitive topic feel clinical and calm. The 'Measure. Calculate. Try on.' illustration gives it personality without clutter, and the black primary button plus the privacy note beneath it is a well-placed trust cue. The problems are execution-level: the copy repeats 'bra size calculator' in nearly every sentence, the international size chart is clipped at the bottom with an inner scrollbar, and footnotes are small and light grey. Usability is solid on the happy path — three modes, in/cm toggle, country selector, and an example path — but the guidance first-timers actually need is tucked behind disclosure triangles, and the lower half stacks paragraphs and tables with little breathing room.
Speed & Security
Speed is the standout: Lighthouse 100/100 on mobile and desktop, LCP 928ms, CLS 0, TBT 0ms. There is no heavy SPA, no bloat, and no reason to expect lag. Security is more mixed. The good: HTTPS enforced with HSTS, X-Content-Type-Options and Referrer-Policy set, and the product's core promise — measurements processed locally, no account, no uploads — is a genuine privacy advantage over brand-run tools. The gaps: no CSP, no frame protection, no Permissions-Policy, and no SPF or DMARC records, which leaves the domain open to spoofing. There is no security page, no privacy policy depth beyond a one-line claim, and no audit or bug bounty. For a tool handling body measurements, the privacy story deserves more than a sentence under a button.
Accessibility & Growth
Accessibility scores well on automated checks — Lighthouse 100/100 — with a single failing audit about visible text labels not matching accessible names, which is a fixable detail rather than a systemic issue. What's missing is the human layer: no accessibility statement, no WCAG conformance claim, and an English-only interface despite serving five sizing systems. Growth is the most interesting question. The problem is real and specific: US, UK, EU, FR and AU labels don't agree, and guessing leads to returns. The alternatives each have a weakness this product exploits — r/ABraThatFits is deep but utilitarian, ThirdLove is polished but brand-biased, Calculator.net is basic. This tool's wedge is neutrality plus privacy plus a try-on journal, all free. That's a coherent reason to exist. The limit is monetization and reach: a free, no-account tool has no obvious revenue path, and the domain is brand new. The idea can grow; the business model is the open question.
Conclusion
If you've ever stood in a fitting room wondering whether a 34D is the same as a 75D, this tool answers that in seconds, for free, without asking for your email. That's worth something. The next step is turning a good calculator into a trusted one: publish a real privacy page, fix the clipped chart, surface the guidance, and add the security headers that match the privacy promise. The bones are good. The polish is the work.
Suggestions for improvement
- Publish a real privacy and security page detailing local-only processing, data handling, and header configuration.
- Fix the clipped international size chart and replace the inner scrollbar with a full-height table.
- Surface the 'Not sure where to start?' guidance by default instead of hiding it behind disclosure triangles.
- Add CSP, frame protection, Permissions-Policy, SPF and DMARC to match the privacy positioning.
Alternatives comparison
Named competitors, point by point. Nobody paid to appear here or to be left out.
 Bra Size Calculator |  A Bra That Fits Calculator | ThirdLove Fit Finder |  Calculator.net Bra Size Calculator | |
|---|---|---|---|---|
| Price | Free | Free | Free (retailer tool) | Free |
| Measurement depth | Quick (2) or six-measurement mode | Six-measurement method | Quiz-style, brand-specific | Basic band/cup math |
| International label conversion | US, UK, EU, FR/ES/BE, AU/NZ | Multiple systems, community-driven | Brand's own sizing only | Limited / basic |
| Sister size suggestions | Yes, with fit checker | Yes | No | No |
| Privacy / no sign-up | Local-only, no account | No account | Retailer data collection | No account |
| Try-on journal | Yes, local journal | No | No | No |
A Bra That Fits Calculator
The well-known community-built calculator from the r/ABraThatFits subreddit, using a detailed six-measurement method. Great for enthusiasts who want deep sizing detail, though its interface is more utilitarian.
ThirdLove Fit Finder
A brand-run quiz-style fit tool from lingerie retailer ThirdLove. It's polished and quick but geared toward recommending that brand's own products rather than giving a neutral, cross-brand size.
Calculator.net Bra Size Calculator
A general-purpose calculator site with a simple bra size tool. It handles basic band and cup math but lacks the measuring guide, sister sizes, and international label comparison.
Comparing options? See Bra Size Calculator alternatives, scored side by side
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