👙 Premium Lingerie Fitting & Measurement Tool
Find your true bra size in seconds using accurate underbust and bust measurements. Includes sister size recommendations, cup volume calculations, and full US, UK, EU, FR, AU, JP conversion charts.
How to Measure Your Bra Size Accurately at Home
Over 80% of women wear the incorrect bra size, often wearing a band that is too loose and cups that are too small. An ill-fitting bra can cause back pain, shoulder strain, and discomfort throughout the day. Our Bra Size Calculator uses professional bra fitting algorithms to find your ideal band and cup combination.
Two Steps to Find Your True Bra Size
1. Measure Your Underbust (Band Size)
Wrap a soft tape measure directly under your bust around your ribcage. Keep the tape parallel to the floor and pull it snug. This measurement determines your band size.
2. Measure Your Bust (Cup Size)
Wrap the tape measure around the fullest part of your bust (usually across the nipples). Keep the tape level and loose without compressing the tissue.
3. Calculate Cup Difference
Subtract your underbust measurement from your bust measurement. Each 1-inch difference represents one cup size (1" = A cup, 2" = B cup, 3" = C cup, 4" = D cup, 5" = DD/E cup).
Understanding Bra Sister Sizes
Sister sizes are bra sizes that hold the same cup volume even though the band size changes. For example, a 34C holds the exact same amount of breast tissue as a 32D (tighter band) and a 36B (looser band).
Frequently Asked Questions (FAQ)
How should a bra fit properly around the band?
The band provides 80% of your bra's support. It should rest firmly and horizontally across your back without riding up. You should be able to slide no more than two fingers under the band.
Why does my cup size change when I change band size?
Cup sizes are proportional to band sizes, not absolute volumes. A 36D cup is significantly larger in volume than a 32D cup because cup depth is calculated relative to ribcage circumference.
