DD Cup Bra Size: What Double D Really Means

A DD cup, or double D, means your bust measures about 5 inches more than your band. It’s the fifth cup step after A, B, C and D. DD is labeled the same in US and UK sizing.

What does DD mean?

DD is a cup letter that describes the gap between your bust and your band. Each step is about an inch: D is 4 inches, DD is 5, and the next cup (DDD in the US, E in the UK) is 6.

After DD the two systems split. UK brands go to E, then double later letters too (FF, GG, HH). Most US brands add another D (DDD) and then jump to G. Our bra size converter shows every system side by side.

Is a DD cup big?

Not necessarily. Cup volume depends on the band. These sizes all share the same cup volume:

• 30DD = 32D = 34C = 36B
• 34DD = 36D = 38C = 40B

So a 30DD is a fairly modest size, while a 40DD is a full one. The letter tells you the shape of the measurement gap, not how big the breasts are on their own. That’s also why many people who wore 34B with a loose band get refitted into a smaller band with a DD cup.

DD cup sizes across bands

See our 34DD bra size guide for the most searched DD size.

DD vs E vs DDD

This is the most confusing step on the size chart:

• US DD and UK DD are the same cup: 5 inches.
• “E” on some labels means DD. ThirdLove’s chart shows “E (DD)”, and Victoria’s Secret uses “DD (E)”.
• UK E is one cup bigger, the same as US DDD: 6 inches.

So if you’re a 34DD and a UK brand sells 34E, that bra is a cup bigger than you need. Our DDD bra size guide covers the next step.

How should a DD bra fit?

• Band: firm and level, on the loosest hook when new. At DD, the band carries most of the weight.
• Cups: no overflow at the top edge or under the arm.
• Wires: sit behind your tissue at the sides, on your ribcage.
• Center gore: lies flat. If it lifts, the cups are too small or too shallow.
• Straps: wider straps spread the load; they shouldn’t leave grooves.

Something off? The bra fit checker explains the likely cause.

Where to find DD bras

Most mainstream brands stock DD. Brands built around fuller busts, such as Freya, start their ranges lower (Freya’s starts at B) and run well past DD, so you get more shapes to choose from. Look for seamed cups, side support panels and three-hook bands. Our bras for large breasts guide explains why those features matter.