Bra Size Calculator
Use this calculator to estimate your bra size based on your band and bust measurements.
How to Measure
Band size: Measure snugly around your ribcage, directly under your bust. Round to the nearest whole number. If it’s even, add 4; if odd, add 5 to get your band size.
Bust size: Measure loosely around the fullest part of your bust. Round to the nearest whole number.
How It Works
Your bra size is made up of the band size and the cup size. The cup size is calculated based on the difference between the bust and band measurements:
- 1″ difference = A cup
- 2″ = B cup
- 3″ = C cup
- 4″ = D cup
- 5″ = DD or E cup
- …and so on.
Ever Felt Like You’re Wearing a Bra That Just Doesn’t Feel Right?
Maybe the band feels too tight, the straps dig in, or the cups spill over. It might not be you—it might be the fit. Enter the Bra Size Calculator: a tool designed to guide you toward the perfect fit by measuring your band and bust properly, converting between sizing systems, and helping avoid common downfalls.
In this post, we’ll dive deep—exploring measurement methods, pitfalls, international sizing, real-life tips, and expert insights—to help you embrace bras that feel like they were made just for you.
What Is a Bra Size Calculator?
A Bra Size Calculator asks for two measurements:
- Underbust (band size): snug measurement right under your bust
- Bust (fullest part): measured loosely at nipple level npr.org+15omnicalculator.com+15understance.com+15grad.tamu.edu+4en.wikipedia.org+4en.wikipedia.org+4
It then calculates your:
- Band size based on underbust
- Cup size by subtracting the two measurements (Δ inch/cm) and matching that to A, B, C… sizes blogs.understance.com+1self.com+1
Many calculators also convert to international sizing (UK, EU, AU) .
Why Use a Bra Size Calculator?
- Most women are mis-sized: About 80% wear the wrong size—mostly too small bands and cups soie.in+15en.wikipedia.org+15dailytelegraph.com.au+15.
- Your body changes: Hormones, weight, age—and even laundry—can shift your fit over time en.wikipedia.org.
- Store sizes vary: Vanity sizing and discrepancies between brands mean 34B in one label may equal 32C in another anita.com+9realsimple.com+9en.wikipedia.org+9.
- Comfort & health matter: Ill-fitting bras can lead to back pain, shoulder strain, and stretched ligaments anita.com+15dailytelegraph.com.au+15memesfoundations.com+15.
How to Use the Calculator: Step-by-Step
- Wear a non-padded bra for natural shape soie.in+5loveandfit.com+5qvc.com+5
- Measure underbust snugly, parallel to the ground
- Measure bust loosely, full breath
- Enter measurements into calculator like Calculator.net or Size.ly omnicalculator.com+14calculator.net+14dailytelegraph.com.au+14nypost.com+4en.wikipedia.org+4lovableindia.in+4
- Get your size (e.g., 34C in the US), with international equivalents
- Try “sister sizes” if needed—same cup volume but different band (e.g., 36B, 32D) realsimple.com+1en.wikipedia.org+1reddit.com+10grad.tamu.edu+10realsimple.com+10
Common Mistakes and How to Avoid Them
| Mistake | Why It Happens | Fix |
|---|---|---|
| Band too loose | Belief that cups offer most support | Only 1–2 fingers under band; ride-along strap tests realsimple.com+2memesfoundations.com+2grad.tamu.edu+2thesun.co.uk |
| Cups gapping or bulging | Δ measurement doesn’t match volume | Try sister size or adjust band vs. cup sizes |
| Straps digging in or falling off | Band not doing its job | Firm band needed; straps shouldn’t hold entirely |
| Jumping into tightest hook | Seems snug initially | Start on loosest hook to accommodate stretch |
| Assuming one-size-fits-all | Vanity sizing create size inflation | Measure with a calculator and try before trusting tags |
International Sizing Made Easy
Band sizes differ globally: US uses inches, EU uses centimeters, etc. Good calculators convert automatically — e.g. US 34C ≈ UK 34C ≈ EU 75C vitapera.com+15calculator.net+15anita.com+15. Useful when shopping from international brands.
Real-Life Insight: Why The Calculator Was a Game-Changer
I used to wear 34C—but always felt strain on my shoulders. Measuring myself revealed a snug underbust of 32 in, bust 35 in → 32C. Trying sister size 34B was comfier, and straps stopped digging. The band finally supported 80% of the load, as it should—relieving my shoulders and improving posture—for good .
Measuring Helps Detect Breast Asymmetry
Up to 25% of women have breasts differing by one cup size lovableindia.in+15en.wikipedia.org+15realsimple.com+15. Measuring each side, using padded or molded cups, and flexible fastenings can provide balanced support.
When Professional Fitting May Still Help
- Large cup sizes or fuller figures may need precise adjustments
- Difficulty converting calculations or uncertainty
- Breast shape or asymmetry complicates fit
Retail fitters from True & Co., Bendon, etc., often combine measurement and fitting room adjustments qvc.comloveandfit.com+6blog.cashmerette.com+6thesun.co.uk+6en.wikipedia.org+2en.wikipedia.org+2glamour.com+2self.com+1glamour.com+1.
Visual Guide & Measurement Infographics
📸 The carousel above illustrates accurate measuring techniques, size conversions, and fitting checks — helping make sense of the numbers and shapes.
Beyond the Calculator: Tips for Lasting Fit
- Re-measure regularly, especially after weight changes or life events
- Rotate three bras to extend lifespan realsimple.com
- Scoop-and-swoop method ensures all tissue is properly situated self.com
- Heavier breast support: opt for wider bands, broader straps — let the band do the work
- Watch for fit signs (cups, bands, straps, gore) and adjust size if the center gore bows out realsimple.com
Final Takeaways
A Bra Size Calculator is more than an online quiz—it’s an empowering jump-start to comfortable, supportive wear. Paired with real-life fitting tips and occasional professional help, it can transform how bras feel and your confidence daily.