A Comprehensive List of Bra Sizes

Bra sizing — is it really as easy as learning your ABCs and 123s? Well, maybe not quite child’s play, but we can certainly help demystify this somewhat complicated system, which tends to vary from style to style and even brand to brand, especially when it comes to European manufacturers.

In the simplest terms, the U.S. uses letters A through F and so on, to represent cup size with incremental increases in volume the further up you go. Multiple lettering, such as AA and DDD, is part of the nuanced system too, which we’ll get into later. A bra’s numerical value indicates its band size, a calculation in inches based on the measurement around a woman’s torso just under her breasts. These numbers typically start at 30 and increase by twos: 32, 34, 36… you get the idea.

So how do you navigate this alphanumeric roadmap? Let’s start with an overview of the most common sizing available from a wide variety of retailers.

Finding Band and Cup Size

The band measurement and cup volume are the two key components, both crucial to determining your best-fitting bra. Together, these should guide you to a size that provides optimal support and comfort, while ensuring a great fit without any spillage or gapes.

Determining a woman’s ideal bra size requires a combination of three separate measurements — the bust, the under-bust and the cup. All that’s needed to do this at home is a ribbon tape measure and a lightly lined bra, which will hold the breasts in their most natural, non-lifted position.

Under-Bust Measurement

Start by wrapping the tape measure around the torso just beneath the breasts. The tape should rest flat against the body, running parallel to the bottom edge of your bra band. If the measurement falls between whole numbers, round up. Add four inches to the number if it happens to be even; add five if it turns out odd. This is your band size. For example, with an under-bust number of 30, the expected band size will be a 34, whereas a 31-inch measurement would give you a band size of 36.

Getting an accurate number will help ensure your bra fits snugly to support breasts, however, it won’t be so tight that it’ll cut into skin or inhibit your ability to easily move and breathe. Because underbands naturally stretch out over time, remember to hook your bra closed on the loosest setting and only increase the tension with repeated wear.

Bust Measurement

The next measurement you’ll need will be the fullest part of the bust. To determine this, simply wrap the tape measure around breasts where they protrude most, making sure to keep the ribbon flat and parallel to your bra’s underband. The difference in inches between the breast and under-bust will be what determines your cup size. Knowing this, you’ll have an accurate sense of the volume needed to avoid overflow or gaping, which happens when you’re wearing a cup that’s too small or too large for your chest.

Cup Size

So, how do you know what cup size you are? Every letter grade is equivalent to the difference of one inch between the breast and under-bust calculations, starting with an A. That means a two-inch difference will result in a B cup, a three-inch difference is a C, and so on up through the alphabet. You might think that multi-letter sizes such as DD represent that cup volume, doubled — a common misconception, but these sizes are actually just midpoints between letter grades. As an example, a DD is a cup that falls halfway between a D and an F, reflecting a five-inch difference between a woman’s breast and under-bust measurements.

Once you have your numbers tallied, you can apply this sizing know-how to any style bra, keeping in mind that oftentimes, slight variations will occur from one manufacturer to another. Trying on a few bras within your size range to determine which fits your body shape best is always recommended, as is exploring the concept of sister sizing.

Standard Sizing

For some types of undergarments, like unstructured bras, tanks and bodysuits, manufacturers may choose to go the grouped sizing route, similar to the standards used in clothing. These include: small, medium and large, with XS and XL bookending each side of the range, as well as plus sizes of 1X, 2X and so on. The groupings are based on the band’s width rather than cup’s volume, meaning that letter grades are less relevant in this type of sizing.

With standard sizing, you can expect a 32C and a 32D to be bracketed together as a Small, a 34C and a 34D to both be Medium, a 36C and 36D to equate a Large, and so on, up through the fit range.

Knowing how your body’s proportions relate to sizing conventions will help take some of the guesswork out of finding your ideal bra. Keep in mind that fluctuations will naturally occur over a woman’s lifetime, such as volume loss due to age, hormonal shifts as a result of pregnancy and nursing as well as weight changes from switch-ups to your diet and exercise routines. What that means is that it is important to retake your measurements each time you shop for new bras, since figuring out your size is an always-evolving process.