Lingerie sizing uses two systems for a reason: band-and-cup sizes (32B, 34C) fit structured bras where support comes from precise fit, while S-M-L sizing fits stretch pieces where the fabric adapts to you. Neither is "more accurate" — they solve different problems. Add international conversion (a US 34 is an EU 75 and a FR 90) and most sizing confusion dissolves.
We use both systems across our own pieces, deliberately. This guide explains when each one appears, why, and how to convert between countries without guessing.
Why Some Bras Say 34B and Others Say M
Look inside the construction and the logic shows itself. Our Esme set runs 32A through 38C because it is engineered: whisper-thin cups on a soft W-support wire, figure-8 straps, a three-row closure. Support pieces like that hold you at two exact measurements — the ribcage circumference (band) and the difference between bust and ribcage (cup). Two numbers, two dimensions, no shortcuts.
Our Colette halter runs S through XL instead — because its stretch lace and halter tie adapt across a range of shapes. When fabric does the adjusting, band-and-cup precision adds cost and complexity without adding fit. The honest rule we design by: wired and structured → band and cup; soft, stretchy, unstructured → S-M-L. If you ever see a heavily structured underwire bra sold only in S-M-L, be suspicious — someone saved money on grading, and your ribs will find out where.
Band and Cup in 60 Seconds
The band number is your underbust measurement. The cup letter is not a fixed volume — it is the difference between bust and band. Each inch of difference steps one letter: 1" = A, 2" = B, 3" = C, 4" = D. This is why a 32D and a 36B can hold a similar volume on different frames — and why cup letters mean nothing without their band number. If that surprises you, sister sizes is the next five minutes well spent.
International Conversion Table
| US band | UK band | EU band | FR / ES band | IT band |
|---|---|---|---|---|
| 30 | 30 | 65 | 80 | 1 |
| 32 | 32 | 70 | 85 | 2 |
| 34 | 34 | 75 | 90 | 3 |
| 36 | 36 | 80 | 95 | 4 |
| 38 | 38 | 85 | 100 | 5 |
Bands are the easy half. Cups are where conversions bite: US and UK agree up to D, then diverge — a US DD is usually a UK DD, but a US DDD is a UK E, and European systems letter continuously (D, E, F) without doubling. Rule of thumb when shopping across systems: convert the band with the table, then re-measure for the cup rather than trusting the letter to travel. A French 90C is a US 34C in theory; in practice, French cups often run one degree shallower in fit.
S-M-L Pieces: How to Choose Without a Cup Letter
For stretch pieces, one measurement dominates: whichever of your bust or underbust sits closer to the top of a size range, follow it. Stretch fabric forgives downward, not upward — an M that is slightly roomy still sits and supports; an M that is slightly small cuts in at exactly the places lace should lie flat. If you are between sizes in a soft piece, take the larger. (In wired pieces, the opposite advice usually applies: the snugger band, because bands stretch with wear.)
FAQ
What size is a US 34B in European lingerie?
A US 34 band is an EU 75 and a FR 90. The B cup usually carries over directly at this size — an EU 75B or FR 90B — though French cuts can run slightly shallower in the cup, so re-measuring beats trusting the letter.
Why do some brands only use S, M, L for bras?
For unstructured, stretch styles — bralettes, triangle cups, halters — fabric elasticity covers several band-cup combinations, so S-M-L works honestly. For structured wired bras, S-M-L is a cost shortcut that sacrifices fit precision.
How do I measure myself at home?
Two tape measurements: snug around the underbust (band), and relaxed around the fullest point of the bust. The difference in inches gives the cup: 1"=A, 2"=B, 3"=C, 4"=D. Our step-by-step measuring guide walks through it with photos, and our fit guide maps results to each piece.
Is lingerie sizing the same as regular clothing sizing?
No. A clothing M and a lingerie M are graded on different measurements — lingerie S-M-L follows bust and underbust, while clothing sizes weight shoulders, waist, and hip. Check the size chart on each product page rather than assuming your dress size.
Every set in our lingerie collection lists its full size run and which system it uses — because the system itself is information about how the piece will hold you.
