K Cup Bra Size: What It Means and Where to Find It

A US K cup means your bust measures about 11 inches more than your band. In UK sizing that cup is H. A UK K cup is 15 inches, which US brands call O.

US K vs UK K

Because US and UK letters split after DD, they’re four letters apart by the time you reach K:

Some UK brands skip the letter I in EU sizing, so their EU labels run one letter later. Our bra size converter flags those differences.

US K cup sizes across bands

The underbust follows the band. A 34K holds roughly the same as a 36J or 32L. The sister size calculator shows the full family.

Who makes K cup bras?

K cups are made mostly by brands that focus on fuller busts:

• Freya: its UK site lists cups B to K, and its US site describes the same range as B to O in US letters.
• Panache: its UK site describes a range up to K, and its US site up to O.
• Curvy Kate: lists cups D to K.
• Victoria’s Secret: states a range of A to O, though not every style comes in every size.

So a US K (UK H) sits comfortably inside these ranges, while a UK K (US O) is at the top. Check the product page, since not every style comes in every cup. Our biggest bra size guide covers what lies beyond.

How do you know you’re a K cup?

1. Measure snugly around your ribcage under your bust. Round up to the next even number.
2. Measure around the fullest part of your bust with a relaxed tape. Leaning forward slightly can help you find the fullest point.
3. Subtract band from bust. 11 inches is a US K (UK H). 15 inches is a UK K (US O).

If both measurements are hard to take alone, ask someone to keep the tape level at the back. The guide to measuring your bra size shows how.

What to look for in a K cup bra

• Firm, deep band with at least three hooks.
• Seamed cups with a side support panel to bring tissue forward.
• Wide, cushioned straps, set so they stay on your shoulders.
• Wires that sit behind your tissue at the sides, not on it.
• Full or balconette coverage that holds everything when you lean forward.