Measure on bare skin or a thin, unpadded bra
Keep a soft tape level and untwisted. Measure the underbust directly below the breast root. For bust measurements, pass the tape around the fullest point without compressing tissue.
Measurements stay on this device
Bra Size Chart & Calculator
Enter two measurements for a fast starting size, or use six measurements for a more considered estimate. Then convert, compare sister sizes, and check the fit.
International notation
Bra size conversion chart
Choose the size printed on a bra, then compare the same canonical band and cup-volume step across seven systems. Always check the brand’s own chart before buying.
Equivalent notation
Choose a size
Seven labels, one shape
This browser cannot show the 3D form. The equivalent notations above describe the same single shape.
These are notation equivalents generated from a shared band and cup index. A brand may grade cup depth, wire shape, or stretch differently.
Filterable table
Conversion rows
Keep approximate cup volume
Sister size calculator
Move down a band and up a cup, or up a band and down a cup. The cup volume stays similar, but the bra’s geometry and feel can still change.
Volume ladder
Nearest sister sizes
Same volume, different band — in 3D
This browser cannot show the 3D comparison. The ladder above lists the same sister sizes.
Tighter band: subtract one band step and add one cup step.
Looser band: add one band step and subtract one cup step.
Use one step first. Several sister-size steps can noticeably change wire width, strap placement, cup height, and support.
Troubleshoot one change at a time
Bra fit checker
Select the current size and every symptom that applies. The tool will rank the next fitting experiments and separate size problems from likely shape or adjustment problems.
Ordered experiments
Try these changes in order
Printable reference
Bra size charts
Compare band notation, cup sequences, measurement differences, and a selected size ladder. Cup letters are relative to the band; they are not fixed volumes by themselves.
Interactive 3D explorer
Step through sizes without reading a table
Reference view
International band chart
US and UK bands share inch-based labels. EU and Japan use metric band labels; French notation adds 15 to the EU label.
From label to real fit
How to measure and use a bra size chart
The number is a band reference. The cup letter describes a volume step relative to that band. A useful fitting process measures, tries, isolates the problem, and changes one variable at a time.
Start on the loosest comfortable hook
A new band should sit level and feel secure on the loosest hook, leaving room to use tighter hooks as elastic relaxes. The straps should fine-tune the fit rather than carry most of the support.
Use conversion as notation, not a fit guarantee
International charts can align band and cup steps, but they cannot make two brands use the same wire width, cup depth, stretch, or grading. Check the exact product chart and returns policy before buying.
Compare a size and a shape
Gapping does not always mean the cup is too large, and tightness does not always mean the band is too small. A cup that is too shallow or too small can pull the band tight; a tall or open cup can gap despite adequate volume.
No account. No body upload.
Private by design
All sizing math runs in your browser. Measurement values are not stored, sent to the application server, placed in a URL, or included in telemetry. A copied share link contains only the selected size and sizing system.