How to Measure For Your Bra Size
Getting accurate measurements is the first step to finding a comfortable bra. It's best to measure while wearing a non-padded, non-compressive bra, or no bra at all. Use a soft measuring tape.
- Measure Your Band Size: Wrap the measuring tape snugly around your ribcage, directly underneath your bust where the bra band would sit. Make sure the tape is level all the way around and parallel to the floor. Exhale to get the smallest possible measurement. Round to the nearest whole number and enter it above.
- Measure Your Bust Size: Wrap the measuring tape loosely around the fullest part of your chest (usually at the nipple level). Make sure the tape is level and not too tight. Round to the nearest whole number and enter it above.
Understanding Your Bra Size Calculation
A bra size has two components: the band size (the number) and the cup size (the letter).
- The Band Size (Number): This is based on your underbust measurement. Our calculator uses a modern fitting method where your underbust measurement is rounded to the nearest even number. This provides a firm, supportive foundation.
- The Cup Size (Letter): This is determined by the difference between your bust measurement and your calculated band size. Each inch of difference typically corresponds to one cup size (1" = A, 2" = B, 3" = C, etc.).
What Are Sister Sizes?
No two bodies are the same, and different bra brands can fit differently. If your calculated size doesn't feel quite right, you should try its "sister sizes". Sister sizes are alternative sizes where the cup volume stays the same, even though the band and cup letter change.
The rule is simple:
- If you go up one band size, go down one cup size. (e.g., 34C has the same cup volume as 36B).
- If you go down one band size, go up one cup size. (e.g., 34C has the same cup volume as 32D).
Our calculator provides your potential sister sizes to give you more options when shopping. Keeping track of your health metrics is important, and you might also find our other Fitness & Health calculators useful.
Signs of a Poorly Fitting Bra
- The band rides up your back (it's too loose).
- Straps dig into your shoulders (the band isn't providing enough support).
- Your breasts spill out of the top or sides of the cups (cups are too small).
- There are gaps in the cups (cups are too large).
- The center panel (gore) doesn't sit flat against your breastbone.