Choose your measurement unit and band calculation method, then enter your underbust and bust measurements. The calculator instantly estimates your band size, cup size, and full bra size, with tips on sister sizing and brand variations.
Free Online Utility Tools
Bra Size Calculator
Instant · Accurate · No Sign‑Up Required
Introduction
Finding the right bra size is essential for comfort, support, and confidence. Our free Bra Size Calculator guide explains how to measure yourself accurately and determine your correct bra size using different international sizing systems. Whether you’re shopping online, updating your wardrobe, or just curious, this guide provides clear measurement instructions, calculation methods, and conversion tables for US, UK, EU, and other regions.
This comprehensive guide includes step‑by‑step measurement techniques, cup size charts, and international size conversion tables. It runs entirely in your browser, keeps your data private, and requires no sign‑up. Combine it with our shoe size conversion for complete wardrobe planning, or our conversion calculator for other unit conversions.
What Is a Bra Size Calculator?
A Bra Size Calculator determines your correct bra size based on two key measurements: the band size (around your ribcage under the bust) and the bust size (around the fullest part of your chest). The difference between these two measurements determines the cup size, while the band measurement (adjusted to the nearest even number) gives the band size. The calculator can also convert between different regional sizing systems (US, UK, EU, FR, AU, etc.).
The guide helps you answer important questions like:
- 📏 How do I measure my band and bust size correctly?
- 👙 What is my cup size based on the difference between bust and band?
- 🌍 How do I convert between US, UK, and EU bra sizes?
- 📏 What does “sister size” mean and how can I use it?
Our Bra Size Calculator guide provides accurate measurement instructions and reference tables. Use it alongside our shoe size conversion or conversion calculator for complete size planning.
Key Features of Our Bra Size Calculator Guide
Get comprehensive bra size guidance with these powerful features:
Step‑by‑step guide to measure band and bust size accurately.
Determine cup size from the difference between bust and band.
Compare sizes across US, UK, EU, FR, AU, and more.
Learn about alternative sizes that provide similar fit.
Works on all devices – phone, tablet, or desktop.
Your measurements never leave your browser – we don’t track, store, or share anything.
No sign‑up, no subscription – use it anytime, forever.
Understand how bra sizing works.
How to Measure for Bra Size
Follow these steps to obtain accurate measurements:
Wear a non‑padded bra. Use a flexible measuring tape, and measure snugly around your ribcage, directly under your bust. Round to the nearest whole number. If it’s even, add 4 inches; if odd, add 5 inches to get your band size (for traditional US/UK). Some modern methods use the ribcage measurement rounded to nearest even number directly.
Measure loosely around the fullest part of your bust, keeping the tape parallel to the floor.
Subtract band size from bust size. The difference in inches determines the cup size: 0 = AA, 1 = A, 2 = B, 3 = C, 4 = D, 5 = DD/E, 6 = F/DDD, etc.
Note: Measurement methods vary by brand. Always refer to the brand’s specific size guide when purchasing.
Cup Size Chart (Difference in Inches)
The following table shows standard cup sizes based on bust–band difference:
| Difference (inches) | US Cup Size | UK Cup Size |
|---|---|---|
| 0 | AA | AA |
| 1 | A | A |
| 2 | B | B |
| 3 | C | C |
| 4 | D | D |
| 5 | DD/E | DD |
| 6 | F/DDD | E |
| 7 | G | F |
| 8 | H | FF |
International Bra Size Conversion (Approximate)
Bra sizes vary across regions. The table below gives approximate conversions for a common size:
| US/UK Band | EU Band | FR Band | AU/NZ Band | Example |
|---|---|---|---|---|
| 32 | 70 | 85 | 10 | 32B → 70B → 85B → 10B |
| 34 | 75 | 90 | 12 | 34B → 75B → 90B → 12B |
| 36 | 80 | 95 | 14 | 36B → 80B → 95B → 14B |
| 38 | 85 | 100 | 16 | 38B → 85B → 100B → 16B |
Note: Cup letters usually remain the same across regions, but UK and US may differ for sizes above D (e.g., UK DD = US DD/E, UK E = US F). Always check brand guidelines.
Example Bra Size Calculation
Assume a person measures 31 inches under the bust (band) and 36 inches around the fullest part (bust):
| Measurement | Value | Calculation |
|---|---|---|
| Band measurement | 31 inches | Odd → add 5 → 36 (band size) |
| Bust measurement | 36 inches | |
| Difference | 36 − 36 = 0 inches | Cup size AA |
| Result | 36AA | US/UK sizing |
Sister Sizes
Sister sizes are alternative bra sizes that have the same cup volume but different band sizes. They are useful when a particular band size is too tight or loose.
- Go up a band size, go down a cup size: e.g., 34B → 36A
- Go down a band size, go up a cup size: e.g., 34B → 32C
This concept is helpful when you find the cups fit well but the band is uncomfortable.
Advanced Features That Make Bra Size Calculation Easy
Our Bra Size Calculator guide includes thoughtful features to help you find the perfect fit:
- Measurement Tips: How to avoid common measuring mistakes.
- Sister Size Reference: Understand alternative sizes for better comfort.
- International Charts: Convert between major sizing systems.
- Brand Variation Note: Reminder that sizes vary by brand and style.
- Integration with Other Tools: Combine with our shoe size conversion for complete outfit planning.
How to Use the Bra Size Calculator Guide
Follow these steps to find your bra size:
Wear a non‑padded bra, measure around your ribcage just under your bust. Round to nearest whole number; if even, add 4; if odd, add 5 to get band size.
Measure around the fullest part of your bust, keeping tape parallel to floor.
Subtract band size from bust size; use the difference to determine cup size from the chart.
Use the international conversion table to convert to your region’s sizing.
Advantages and Benefits of Using Our Bra Size Calculator Guide
Why use our guide instead of guessing?
How the Bra Size Calculation Works Internally
The calculation follows these steps:
- Step 1 – Input Band Measurement: Rounded to nearest inch.
- Step 2 – Determine Band Size: Add 4 or 5 inches to even/odd rounded measurement (traditional method) or use direct even round (modern method).
- Step 3 – Input Bust Measurement: Rounded to nearest inch.
- Step 4 – Difference: Bust minus band size.
- Step 5 – Cup Size Mapping: Convert difference to cup letter.
These calculations are performed mentally following the guide, or by the interactive version if available. All processing is client‑side.
Real‑Life Use Cases for the Bra Size Calculator Guide
Here are some common scenarios where this guide is invaluable:
Ensure proper fit when buying from international brands.
Re‑measure after weight changes or pregnancy.
Learn about measurement and international sizing.
Assist customers in retail environments.
Find correct size for athletic support.
Provide size guide on product pages.
Why Choose Our Bra Size Calculator Guide Over a Spreadsheet?
Spreadsheets lack the contextual measurement instructions. Our guide gives you instant, accessible information:
- Instant Reference: All measurement and conversion charts in one place.
- Completely Free: No sign‑up, no ads – use it as often as you like.
- Privacy First: No data entered; your measurements stay private.
- Real‑Time Updates: Easy to refer to while measuring.
- Part of the MathMasterTool Ecosystem: Combine with our shoe size conversion for complete size management.
- Works Offline: Once loaded, works without internet – perfect for use anywhere.
Tips for Getting the Most Out of the Bra Size Calculator
Follow these suggestions for accurate measurements:
- Measure without a bra or with a non‑padded bra: Padded bras can alter measurements.
- Stand upright, breathe normally: Avoid pulling tape too tight.
- Use a flexible measuring tape: Fabric tape works best.
- Re‑measure regularly: Body changes can affect size.
- Check brand charts: Sizes vary; always refer to the specific brand.
Common Mistakes to Avoid When Determining Bra Size
These errors can lead to poor fit:
- Wearing a padded bra while measuring: It adds bulk and distorts bust measurement.
- Measuring bust with the tape too tight: Should be snug but not compressing.
- Using old measurements: Re‑measure regularly.
- Ignoring sister sizes: A sister size might be more comfortable.
- Not converting international sizes: A UK 34B is not the same as EU 34B.
Deep Dive: Understanding Bra Sizing
Bra sizing combines a band size (the underbust measurement adjusted) and a cup size (the difference between bust and band). The traditional method adds 4–5 inches to the underbust to get the band, but many modern fitters use the direct even number. Cup sizes progress in 1‑inch increments. International systems have different band numbering and cup labelling, especially above D. Understanding these nuances helps you navigate the wide variety of available bras.
Key concepts:
- Band Size: The number part (e.g., 34).
- Cup Size: The letter part (e.g., B).
- Sister Size: Different band/cup combo with same cup volume.
- International Conversion: Band numbers differ by region.
Example: A measurement of 32 inches underbust and 36 inches bust yields a 34B (using traditional method) or 32C/D (using direct method), depending on the system.
Our Bra Size Calculator guide helps you interpret these measurements correctly.
Frequently Asked Questions
Conclusion
Finding the right bra size is key to comfort and confidence. Our free Bra Size Calculator guide provides everything you need to measure and convert sizes accurately and privately – no sign‑up required.
As part of the MathMasterTool suite, combine this with our shoe size conversion, conversion calculator, or height calculator for all your sizing needs. Every tool is free, private, and designed to make your life easier.
Start finding your perfect fit today – try the Bra Size Calculator guide now and feel confident in every outfit.
Leave a Reply