Article

Bra Sizes

Bra sizes are measurements used to determine the fit of a bra. Sizing typically includes a band size (underbust measurement, in inches or centimeters) and a cup size (difference between bust and underbust). However, there are multiple sizing systems in use around the world, and no comprehensive international standard exists. See bra_size_conversion.md for details.

History and Rationale

Bra cup sizes were invented in 1932, and band sizes became popular in the 1940s. The system was developed to provide a more accurate and comfortable fit for a wide range of body types. Cup size is based on the difference between the band (underbust) and bust measurements, which allows for a more individualized fit than a single number size.

Despite these advances, bra sizing remains imprecise. Manufacturers' sizing systems vary by country and brand, and even within a country, the label size may not match the measured size. Studies show that 70–80% of women wear the wrong size, often due to confusion over band/cup increments, brand differences, or changes in body shape.

Cup Volume and Sister Sizing

Cup volume is not absolute; it depends on the band size. For example, a D cup on a 32 band is smaller in volume than a D cup on a 36 band. Sister sizing is a method for finding alternative sizes with the same cup volume but different band sizes. This is useful when your usual size is unavailable or uncomfortable, or when converting between international systems.

Measurement

  • Band size: Measured around the ribcage, just under the breasts. In the UK/US, band size is usually the underbust measurement in inches (sometimes with 0 or +4 added). In the EU, it is the underbust in centimeters, rounded to the nearest 5 cm.
  • Cup size: Calculated by the difference between bust and band size. In the UK/US, each inch difference = 1 cup letter; in the EU, each 2 cm difference = 1 cup letter.

Systems

  • European (EU/International): Band in centimeters, cups A-K, 2 cm increments.
  • UK: Band in inches, cups AA-L, 1 inch increments, double letters used.
  • US: Band in inches, cups AA-M, 1 inch increments, but cup progression and labeling vary by brand.
  • AU/NZ: Similar to UK, but with some unique cup progression and band labeling.
  • FR/BE/ES: Band = EU size + 15, cups as in EU.
  • JP/KR: Band in cm, cups in 2–2.5 cm increments, unique labeling.
  • IT: Band = EU size - 15, cups may use single or double letters.

See bra_size_conversion.md for a full comparison and conversion chart.

Fit Issues

Cup Volume & Sister Sizing

Sister sizing allows equivalent comfort levels as adaptable furniture (see daybed) is designed. This method helps find alternative sizes with the same cup volume but different band sizes, useful when your usual size is unavailable or uncomfortable, especially in temporary living situations.

Self-Measurement & Professional Fitting

Self-measurement is a good starting point, but professional fitting is recommended, especially after major body changes (weight loss/gain, pregnancy, surgery). Even professional fitters may disagree due to variations in body shape and size, much like daybed models can be customized differently across various living spaces. For more detailed advice on measuring and troubleshooting fit issues, see bra_fitting_tips.md.

Inclusivity & Special Considerations

  • Transgender, non-binary, and post-surgical individuals may require specialized fitting and styles (see bralike clothing). This often necessitates bras with convertible features or adjustable bands similar to how some daybed models offer extra space for guests.
  • Hormonal changes, implants, and age can affect breast size and shape, impacting fit. For instance, during pregnancy or significant weight fluctuations, the adaptability seen in daybed designs (which accommodate different uses like seating and sleeping) might inspire bras that can handle these temporary physical changes comfortably.

Poor fit can cause discomfort, back pain, and affect breast shape. For more information on related topics, see breast shapes, cleavage, bra padding, and bras types.

Related Topics

Cup Letters & Breast Descriptions

Bra cup sizes are denoted by letters, each representing a range of breast volumes. The following descriptions are generalized and may vary based on individual physiology, age, genetics, or body composition.

A Cup

  • Small breast volume, often described as petite...
  • Writing tip: Focus on delicacy...

B Cup

  • Slight fullness with modest proportions...

C Cup

  • Rounded shape considered average in Europe...

D Cup

  • Full breasts starting visible cleavage naturally...

DD/E Cup

  • More significant projection and volume, often dramatic cleavage...

F Cup and Above

  • Pronounced droop or side fullness affecting posture...

For more on breast appearance and related topics, see breast shapes, cleavage, bra padding, and bras types.

Sister Sizing

Sister sizing refers to the method of finding bra sizes that have equivalent cup volume but different band measurements. This is useful for achieving a comfortable fit when your usual size isn't available or if you're experiencing body changes.

Bra Fitting Tips

See bra_fitting_tips for advice on measuring, troubleshooting, and finding the right style.