The difference between bra cup sizes is determined by the volume of the breast tissue that each cup can accommodate. This difference is standardized, with each cup size representing a specific increase in breast volume. Here's a detailed explanation of how bra cup sizes differ:

Understanding Bra Cup Sizes

1. Measurement Basis:

   • Band Size (Underbust Measurement): The measurement around the ribcage, just under the bust.
   • Bust Size (Overbust Measurement): The measurement around the fullest part of the bust.

2. Calculating Cup Size:

   • Difference Calculation: Cup size is calculated by subtracting the band size from the bust size. The difference in inches corresponds to a specific cup size.

Standard Cup Size Differences

In the UK, US, and many other regions, each cup size increment represents an approximate one-inch (2.54 cm) increase in the difference between the band measurement and the bust measurement. Here's how the differences correspond to cup sizes:

• AA Cup: Less than 1 inch difference
• A Cup: 1 inch difference
• B Cup: 2 inches difference
• C Cup: 3 inches difference
• D Cup: 4 inches difference
• DD (E) Cup: 5 inches difference
• DDD (F) Cup: 6 inches difference
• G Cup: 7 inches difference
• H Cup: 8 inches difference
• And so on...

Example Calculation

1. Measure Your Band Size:

   • Measure snugly around your ribcage, just under your bust. Suppose the measurement is 34 inches.

2. Measure Your Bust Size:

   • Measure around the fullest part of your bust. Suppose the measurement is 37 inches.

3. Calculate the Difference:

   • Bust size (37 inches) - Band size (34 inches) = 3 inches difference.

4. Determine Cup Size:

   • A 3-inch difference corresponds to a C cup size. Thus, the bra size would be 34C.

Sister Sizes

"Sister sizes" refer to bra sizes that have the same cup volume but different band sizes. For example, 34C, 36B, and 32D are sister sizes. If you find a cup fits well but the band is too tight or too loose, you might try a sister size:

• Down a Band Size, Up a Cup Size: 34C to 32D
• Up a Band Size, Down a Cup Size: 34C to 36B

International Variations

Different countries have variations in how they label cup sizes, especially beyond D cups. For instance:

• UK Sizing: Follows the sequence D, DD, E, F, FF, G, GG, etc.
• US Sizing: Often uses D, DD, DDD, G, H, etc., with some brands differing in labelling.
• European Sizing: Typically uses a continuous letter system without double letters, such as D, E, F, G, H, etc.

Visual and Fit Differences

• Incremental Differences: The visual difference between adjacent cup sizes might seem small but can significantly impact fit and comfort. For instance, the difference between a B cup and a C cup is about one inch in bust circumference, which can affect how the bra supports and shapes the breasts.
• Breast Shape and Distribution: Cup size differences are also influenced by breast shape and how breast tissue is distributed, which can affect the fit and appearance of the bra.

Cups measuring and sizing...

The difference between bra cup sizes is based on the volume of breast tissue each cup can hold, with each size increment typically representing a one-inch increase in the bust measurement relative to the band size. Understanding this difference, along with concepts like sister sizes, can help you find the best fitting bra. Always consider both band and cup sizes, and remember that different brands and regions may have slight variations in sizing.