How it works
Estimate bra size based on band and bust measurements.
Input query strings and outputs
Use an input name in this page’s URL as ?name=value, and join additional inputs with &. Portable shared links may instead use the compact ?ac= state parameter.
Input query strings
2-
?band=Underbust (Band)Number · Optional · Default: 34
-
?bust=Bust (Fullest part)Number · Optional · Default: 37
Outputs
1-
resultResultText · Primary output
result contains the calculator’s complete rendered result area, including its visible result cards, tables, charts, and messages.
Estimate your bra size from simple measurements
Description
The Bra Size Calculator is a starting point for finding a well-fitting bra. Because brand sizing can vary significantly, this tool uses the standard US systematic approach to provide an estimate. By taking two simple measurements—your underbust (band) and the fullest part of your chest (bust)—you can identify your likely band number and cup letter.
Inputs
- Underbust (Band): Measure around your chest, directly under your breasts (in inches).
- Bust: Measure around the fullest part of your breasts (in inches).
Outputs
- Estimated Size (US): A combination of the band number and cup letter (e.g.,
34C).
Chart
- N/A: This tool provides a direct alphanumeric size estimate.
“Good to Know”
- The Band Rule: In this calculation, band sizes are always even numbers. If your underbust measurement is odd, the tool automatically rounds up.
- The Cup Formula: Cup size is determined by the difference between your bust and your band. A 1-inch difference is an ‘A’, 2 inches is a ‘B’, 3 inches is a ‘C’, and so on.
- Fit Tip: A good bra band should be level all the way around and firm, but you should be able to slide two fingers under it. If the band rides up in the back, it’s likely too large.
Examples
Example 1: Standard Fit
- Input: Band: 34, Bust: 37
- Output: 34C (37 - 34 = 3, which is the 3rd letter)
Example 2: Small Band, Medium Cup
- Input: Band: 30, Bust: 34
- Output: 30D
Example 3: Even Difference
- Input: Band: 36, Bust: 39
- Output: 36C