The Mathematics of Sizing

It is estimated that over 70% of women are wearing the wrong size. This massive statistical error is not due to bad measurements, but rather terrible mathematics forced upon the market by major clothing retailers.

The modern, mathematically accurate system (often referred to online as the A Bra That Fits method) relies on a simple +0 formula:

1. Band Size: Your snug underbust measurement, rounded to the nearest even number.
2. Cup Size: The mathematical difference between your Bust and your Band. Every 1-inch difference is a cup letter (1" = A, 2" = B, 3" = C, 4" = D, 5" = DD).

The "+4" Retail Scam

If the math is so simple, why is everyone wearing the wrong size? The answer is the outdated +4 Method. In the 1930s, fabrics did not have elastic or spandex. If your ribs measured 32 inches, and you put on a 32-inch band made of stiff, unyielding fabric, you wouldn't be able to breathe. To solve this, manufacturers told women to mathematically add 4 inches to their underbust measurement to create breathing room.

Today, fabrics are incredibly stretchy. A modern 32-inch band can easily stretch to 34 or 35 inches. However, massive retail chains continue to use the +4 method in their fitting rooms. Why? Because it is cheaper for their supply chain. It is incredibly expensive to manufacture a massive matrix of sizes (from 28A to 40K). It is much cheaper to only manufacture sizes 32 to 38 in cups A to DD.

If a woman walks into a store with a 28-inch underbust and a 34-inch bust, the +0 math says she is a 28E. The store doesn't sell that size. So, the clerk uses the +4 method (28 + 4 = 32 band). Now the difference between the 34 bust and the 32 band is only 2 inches. The clerk sells her a 32B. The store makes a sale, but the customer goes home with a band that is 4 inches too big and provides absolutely no support.