Bra Cup Sizes Explained: A to DDD/F
A bra's cup letter is not an absolute size — it's the difference, in inches, between your bust measurement and your band measurement. One inch of difference is an A cup, two inches a B cup, three inches a C cup, four inches a D cup, five inches a DD/E cup, and six inches a DDD/F cup — also commonly called a "triple D" bra size. The same letter means something different on every band size.
Why Cup Size Is Relative, Not Fixed
A 28D and a 36D are not the same size. Both have a 4-inch difference between band and bust, but a 4-inch difference on a 28-inch band is a much smaller actual breast volume than a 4-inch difference on a 36-inch band. This is why buying a D cup without a band number tells you almost nothing about fit.
The Full Cup Letter Scale
- 1/3 inch: AAA cup
- 1/2 inch: AA cup
- 1 inch: A cup
- 2 inches: B cup
- 3 inches: C cup
- 4 inches: D cup
- 5 inches: DD or E cup (same size, different naming convention)
- 6 inches: DDD or F cup, also called a triple D (same size, different naming convention)
DD/E and DDD/F: Why Two Names for the Same Size?
US sizing historically used DD and DDD, while UK and international sizing uses E and F for the same cup volumes. Because the two conventions are used interchangeably across brands and countries, BRABAR labels these sizes as DD/E and DDD/F so there is no ambiguity about which cup you are getting. "Triple D" is simply the spoken-out version of DDD, referring to the exact same size.
Common Misconceptions
An A cup is not always the smallest, and D is not always the largest. A 36A has a larger actual cup volume than a 28A, because cup size is relative to band size, not an absolute measurement.
A D cup does not automatically mean large. A D cup is a moderate, common size once you account for band size — it simply means a 4-inch difference between band and bust, which happens across every band size from 28 to 40 and beyond.
Finding Your Cup Size
Use BRABAR's rib cage method to measure your band size first, then measure your full bust and subtract. The difference in inches gives you the cup letter from the scale above.
Frequently Asked Questions
What is a triple D bra size?
A triple D bra size is the spoken-out name for a DDD or F cup — a 6-inch difference between bust and band measurement. It's the same size whether it's labeled DDD, triple D, or F; the naming just varies by brand and region.
Is a D cup bra considered large?
Not inherently. Cup size only measures the difference between band and bust — a D cup on a 28 band is a different volume than a D cup on a 38 band. Whether a D cup counts as large depends entirely on the band size paired with it.
What is the difference between DD and E cup, or DDD and F cup?
Nothing — they are the same cup volume under two different naming conventions. DD and DDD are common in US sizing; E and F are common in UK and international sizing.
Why is my cup size different in every brand?
Cup sizing is not perfectly standardized across brands, and small differences in how a company measures or grades sizes can shift the letter by one size. Your inch-based measurement stays consistent even when the label does not.
Can a small band have a large cup size?
Yes — a small band paired with a full cup, like 28DDD/F, is common and simply means a large difference between rib cage and bust on a petite frame. This is one of the size ranges most underserved by mainstream sizing. For girls with an especially small rib cage, see Small-Band Bras for Girls and Teens for flexible-fit styles like the Soft Cami Bra Top, where the smallest labeled size accommodates a rib cage a little smaller than the label suggests.
Explore BRABAR's full cup and band size range in our collections, from AA to DDD/F and band sizes 28 to 40.
