Bra Size Calculator

The Ultimate Guide to Finding Your True Bra Size

Studies consistently show that a vast majority of women are wearing the wrong bra size. This can lead not only to discomfort, such as digging straps and poking underwires, but also to poor posture and a lack of proper support. This calculator and guide are designed to empower you with the knowledge to find a starting size that can dramatically improve your comfort and confidence.

How to Measure Yourself Accurately: A Step-by-Step Guide

For the most reliable results, you will need a soft, flexible measuring tape. It's often helpful to perform these measurements while wearing a comfortable, non-padded bra to ensure your bust is supported and positioned naturally.

Step 1: Measure Your Band Size (Underbust)

1. Stand straight and exhale completely. Your lungs being full of air can slightly increase the measurement.
2. Wrap the measuring tape around your ribcage, directly underneath your bust where the bra band would normally sit.
3. Ensure the tape is level all the way around your body (you can use a mirror to check your back).
4. The tape should be snug, but not so tight that it's digging into your skin or restricting your breathing. Read the measurement and enter it into the **"Band Measurement"** field above.

Step 2: Measure Your Bust Size

1. Wrap the measuring tape loosely around the fullest part of your bust, typically across the nipple line.
2. Again, ensure the tape is level all the way around.
3. The tape should be comfortably loose, just skimming the body without compressing your breast tissue. Compressing the tissue will result in an inaccurate, smaller measurement.
4. Read the measurement and enter it into the **"Bust Measurement"** field.

How We Calculate Your Bra Size

Calculating Your Band Size

Bra bands are typically sold in even-numbered sizes (32, 34, 36, etc.). The traditional method, which this calculator uses for a common starting point, involves rounding. We take your raw underbust measurement (in inches) and round it up to the nearest even number. For example, a measurement of 31 inches would be rounded up to a **32 band size**.

Calculating Your Cup Size

The cup size represents the volume of your bust relative to your band size. It's determined by the difference between your bust measurement and your *calculated* band size.

• 1 inch difference = A Cup
• 2 inch difference = B Cup
• 3 inch difference = C Cup
• 4 inch difference = D Cup
• And so on... each inch adds another cup size.

Understanding "Sister Sizes" - The Secret to a Better Fit

**This is one of the most important concepts in bra fitting.** A "sister size" is an equivalent bra size with a different band and cup letter, but the same actual cup volume. This is crucial because if a bra's cup fits you perfectly but the band is too loose or too tight, you can use a sister size to fix the band issue while keeping the cup fit.

The rule is simple:

• If you go **DOWN** one band size, you must go **UP** one cup size. (e.g., from 34C to 32D)
• If you go **UP** one band size, you must go **DOWN** one cup size. (e.g., from 34C to 36B)

All three of these sizes (32D, 34C, 36B) have the same cup volume, but the band length is different. Our calculator provides these sister sizes to give you more options when you're shopping.