40K Bras

In a 40K, the 40 refers to your ribcage measurement and the K to a bust roughly 15 inches larger than it. If you've been fitted in a US brand and are shopping a European label, expect the letter to shift — the volume stays the same, the notation doesn't.

How a 40K should fit

A 40K is a full-bust size, and the engineering matters more than the label. Wide side wings, a firm band with four hooks and seamed cups will outperform a prettier bra with thin straps every time.

Sister sizes to try if 40K isn't right

• Band digs in — 42JJ gives the same cup volume with more room
• Cup gapes at the top — try 40JJ

Best 40K styles

Look for side support panels, which push tissue forward and stop it migrating under the arm — the single most useful feature at 40K. Full cup and balconette shapes both work; strapless is harder at this size and worth trying with a longline style, which spreads the weight across a wider band.