Stop Wearing the Wrong Size
Studies suggest that up to 80% of women wear the wrong bra size, leading to back pain, shoulder indentations, and poor posture. The archaic "Plus Four" measuring method used by many retail stores often results in bands that are too loose and cups that are too small. Our Bra Size Calculator uses raw, direct measurements to find your mathematically accurate true size.
How True Sizing Works
To get the most accurate result, wear an unpadded bra and use a flexible measuring tape. The math relies on the difference between two specific measurements:
- The Band Size (Underbust): Measure snugly directly under your bust, where the bra band sits. Exhale completely to get a firm measurement. Your band size provides 80% of the support for your chest. If the band rides up your back, it is too large.
- The Cup Size (Overbust): Measure loosely around the fullest part of your bust (usually at the nipple line). The tape should not compress the tissue.
- The Calculation: The cup letter is determined by the mathematical difference between these two numbers. A 1-inch difference is an A cup, a 2-inch difference is a B cup, a 3-inch difference is a C cup, and so on.
How to Use This Tool
- Upload or Input Data: Select your file or paste your data directly into the tool interface. Everything remains on your device.
- Configure & Process: Adjust any optional settings if necessary. The tool will process your data instantly inside your browser.
- Download Result: Preview the output and click the download or copy button to save your final results.
Frequently Asked Questions
What is 'Sister Sizing'?
Cup volume is relative to band size. A 34C holds the exact same volume of tissue as a 36B or a 32D. If your 34C fits perfectly in the cups but the band is too tight, you don't need a 36C (the cups will be too big); you need its sister size, a 36B.
Why do Victoria's Secret fitters give me a different size?
Many legacy retail brands still use the 'Plus 4' method (adding 4 inches to your underbust measurement). They do this to squeeze more women into a limited, cheaper-to-manufacture size matrix (32-38 A-DD), rather than stocking true sizes like a 28G.
How should a new bra fit on the hooks?
A brand new bra should fit perfectly on the *loosest* set of hooks. As the elastic degrades and stretches over months of wear and washing, you move to the tighter hooks to maintain support.