How This Bra Size Calculator Works
Determining the correct bra size is essential for ensuring a comfortable fit. Our bra size calculator uses modern measurement standards to help you find bra size equivalents in other countries and clearly explains how to measure bra size step by step. First, hold the tape measure flat and take your snug underbust measurement, then take your fullest bust measurement. Then, select inches or centimeters. The tool automatically converts units and applies the closest even band used in the U.S. measurement system. It then matches the result to sizes corresponding to the U.K., E.U., France, Belgium, Spain, and Australia.
Additionally, we demonstrate the traditional “+4” which was used in old bra size calculator usa guides. This allows you to see the difference between a size recommended by a classic boutique employee and a size recommended by most lingerie brands today. The tool supports decimal measurements, so even if you take measurements with millimeter precision, the result is calculated neatly.
Formula
Band (US) = Round the underbust measurement (in inches) to the nearest even number. Bust = Round the fullest bust measurement (in inches) to the nearest even number. Cup difference = bust measurement minus band measurement. The cup size is selected sequentially based on the cup difference: AA, A, B, C, D, DD, E, F, G, etc. International conversions are based on a special table: EU band: Values such as 60, 65, 70, 75, or the rounded centimeter equivalent; FR/BE/ES: EU band + 15; AU: clothing size equivalents, such as 8, 10, 12, 14, and 16. When the old "+4" method is enabled, four inches are added to the band measurement, and the label is recalculated. This allows the results of both methods to be viewed side by side.
Example: an 85 cm band (33.5 in) becomes a 34 band, a 95 cm bust (37.4 in) rounds to 37, and the difference of three inches yields a C cup. The converter returns US/CA 34 C, UK 34 C, EU 75 C, and FR 90 C. Toggling the legacy view shows 38 C, matching calculators like calculator.net while clarifying why Victoria Secret might list 32DD for the same measurements.
FAQ
Does the bra calculator support decimal values? Yes. It accepts decimal entries such as 33.8 and rounds after converting to inches. This prevents cup size discrepancies.
How often should bra measurements be updated? It is recommended that you measure yourself every three to six months, or after experiencing weight changes, changes in your exercise routine, or hormonal changes. Since the body is constantly changing, a fixed cup size may become invalid over time.
Why do my measurements differ between brands? Some brands' calculators tend to be 2-4 inches smaller than the underbust measurement. This results in a narrower band and a larger cup size. Use our calculated size as a basis. If you want the exact fit that a particular brand provides, reduce the band size and increase the cup size.
Can I shop globally with these measurements? Yes. The calculator converts measurements to EU, US, FR/BE/ES, UK, and AUS standards, so you can easily order from abroad without memorizing conversion charts.
Can I share the page with others? Absolutely. Share it with friends, team members, or customers to simplify bra measurements, make shopping more informed, and reduce return rates.