Bra Calculator

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bra calculator
Inches (US/UK)Centimeters (EU/Intl)
Your Estimated Size:
Enter measurements above
© Calculator Soup Style Bra Calculator
function calculateBraSize(){var u=parseFloat(document.getElementById('underbust').value);var b=parseFloat(document.getElementById('bust').value);var unit=document.getElementById('unit_type').value;var showSteps=document.getElementById('steps').checked;if(isNaN(u)||isNaN(b)){alert('Please enter valid numerical measurements.');return;}if(b<=u){alert('Bust measurement must be larger than underbust measurement.');return;}var band,diff,cup;if(unit==='inches'){band=Math.round(u);if(band%2!==0){band+=1;}diff=Math.round(b-band);}else{var uInch=u/2.54;var bInch=b/2.54;band=Math.round(uInch);if(band%2!==0){band+=1;}diff=Math.round(bInch-band);}var cups=["AA","A","B","C","D","DD/E","DDD/F","G","H","I","J","K"];if(diff=cups.length){cup=cups[cups.length-1];}else{cup=cups[diff];}var finalSize=band+cup;document.getElementById('resultValue').innerHTML=finalSize;if(showSteps){var stepText="Band Calculation: "+band+"
Bust-to-Band Difference: "+diff+" inch(es)
Cup Category: "+cup;document.getElementById('stepDetails').innerHTML=stepText;document.getElementById('stepDetails').style.display='block';}else{document.getElementById('stepDetails').style.display='none';}document.getElementById('answer').style.display='block';}

How to Use the Bra Calculator

Finding the perfect fit is essential for comfort, posture, and confidence. This bra calculator is designed to provide you with an accurate starting point based on standard industry sizing. To get the best results, you will need a flexible measuring tape and a mirror.

Follow these steps to ensure your inputs are accurate:

1. Measure Your Underbust
Exhale and wrap the tape snugly around your ribcage, directly under your breasts. The tape should be level and firm, but not dig into the skin.
2. Measure Your Bust
Measure around the fullest part of your chest (usually across the nipples). Keep the tape parallel to the floor and don't pull it tight—it should just rest on the surface.
3. Select Units
Choose between inches (common in the US and UK) or centimeters (standard for EU and International sizing).

How It Works: The Math Behind the Size

Modern bra sizing is a combination of two measurements. While different brands may vary slightly, the bra calculator uses the standard difference method which is the most widely accepted approach in professional fittings.

Cup Size = Full Bust Measurement – Calculated Band Size

  • The Band Size: Your underbust measurement is rounded to the nearest even number. If your measurement is 33 inches, the band size is typically adjusted to 34.
  • The Cup Size: Each inch of difference between the bust and the band represents one cup size. A 1-inch difference is an A cup, 2 inches is a B cup, 3 inches is a C cup, and so on.
  • Metric Conversion: When using centimeters, the calculator converts the values to inches to align with the standard 1-inch-per-cup-size progression used in US/UK manufacturing.

Bra Sizing Example

Example Scenario: Let's say Sarah wants to find her size using the bra calculator. She measures her underbust and gets 31.5 inches. She measures her fullest bust point and gets 36 inches.

Step-by-step calculation:

  1. Underbust: 31.5 inches. Rounding up to the nearest even number gives a Band Size of 32.
  2. Full Bust: 36 inches.
  3. Calculation: 36 (Bust) – 32 (Band) = 4 inches.
  4. Cup Mapping: A 4-inch difference corresponds to a D cup.
  5. Final Result: Sarah's estimated size is 32D.

Common Bra Fitting Questions

What are "Sister Sizes"?

Sister sizes are groups of bra sizes that have the same cup volume, even though the band size and cup letter are different. For example, if a 34C feels too tight in the band, you might try a 36B. The 36B has the same volume as the 34C but offers a wider band. If the band is too loose on a 34C, you might try a 32D.

Why does the bra calculator give a different size than my current bra?

There are several reasons for this. First, bra materials stretch over time; your current bra may have started as a 32, but now stretches to a 34. Second, different brands use different sizing charts (especially between US, UK, and EU brands). Finally, many people are wearing a band that is too large and a cup that is too small without realizing it.

How often should I recalculate my size?

Experts recommend using a bra calculator every 6 to 12 months. Body changes due to weight fluctuations, hormonal changes, or pregnancy can significantly impact your measurements even if you feel like your clothes still fit the same way.

Tips for a Better Fit

  • The Scoop and Swoop: When putting on a bra, lean forward and ensure all breast tissue is pulled forward into the cup.
  • The Band Rule: The band should be level across your back. If it rides up, the band is too big and you should try a smaller band size.
  • Two-Finger Test: You should be able to fit exactly two fingers under the band comfortably.
  • No Gapping: If there is space at the top of the cup, try a smaller cup size or a different cup shape (like a balcony or plunge style).

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