Bras Size Chart

Two figures on one label, converting on two entirely different logics

A bra size combines a band number (underbust circumference) and a cup letter (a relationship between bust and band), and the two halves of that label convert across US, UK, and EU sizing in genuinely different ways. Band size is a real unit conversion — US and UK state it in inches, EU in centimetres, and the arithmetic behind that is as dependable as the shirt-collar conversion elsewhere on this site. Cup lettering is not arithmetic at all; it's a coded alphabet that the three systems have extended to different lengths.

US cup lettering runs out of room before UK or EU lettering does

The two scales agree cleanly through A to D, then quietly part ways — UK and EU lettering keeps extending past D while the mainstream US convention has historically plateaued around DD, leaving no single agreed US equivalent for a EU or UK F cup. This site's individual bra-size conversion pages walk through what to do about that gap for each specific direction.

Sister sizing means there's rarely one single correct answer

Cup size describes a relationship between band and bust measurement, not a fixed volume — go up one band size and drop the cup letter one step, or the reverse, and the two combinations describe roughly the same actual cup volume. A US 34D and a US 36C, for instance, can represent a similar bust volume on different band sizes. This means converting a single foreign size to a single domestic size is inherently an approximation of a relationship, not a lookup of one fixed number to another, and trying an adjacent sister-size combination is standard practice when a first converted size doesn't fit.

Specialty retailers have closed the lettering gap that mainstream brands haven't

A parallel US fitting industry built around fuller-bust customers has grown specifically to answer this lettering gap, stocking the extended UK/EU-style letters that big-box American brands generally don't — worth trying before assuming your size simply doesn't exist in the US market.

Wire shape and construction vary by regional tradition, independent of the numbers

Underwire geometry is a maker-level design choice, not a labeling one — some continental European houses shape the wire to sit higher on the side or closer to the sternum than typical British or American construction, which is why a correctly converted band-and-cup can still feel different in wire placement depending on which country actually cut the piece.

Band arithmetic is solid, cup letters are not

Convert the band size with confidence, since it's genuine unit arithmetic. For the cup, compare your actual bust-minus-band measurement against the specific brand's own chart rather than trusting a fixed letter-to-letter table, and try an adjacent sister-size combination if your first choice doesn't sit right — the band-and-cup relationship, not the printed conversion table alone, is what actually determines fit.

Wire-free and bralette styles follow looser sizing logic entirely

Everything above assumes an underwired, structured bra with a defined band and cup. Wire-free bralettes and similarly soft, unstructured styles are commonly sized more like a stretch top than a precisely engineered undergarment, tolerating a wider range of actual measurements at one labeled size — the band-and-cup conversion logic this chart covers applies far less precisely to this category.

Sports bras use their own separate sizing convention

High-impact sports bras are frequently sized by a combined band-and-cup range or by a simple S/M/L scale tied to overall compression level rather than the standard band-and-cup system, since the priority is compression and support during movement rather than the precise shaping this chart's numbers assume — converting a standard bra size into a sports-bra size isn't a reliable approach, and checking that specific brand's sports-bra chart directly is the better path.

Nursing and maternity bras add their own separate sizing logic

Nursing bras are commonly sized around your pregnancy or immediate postpartum band-and-cup measurement with room built in for fluctuation, rather than your pre-pregnancy size the way maternity clothing elsewhere on this site typically works — a genuine exception to the usual maternity-sizing rule, worth knowing before assuming the same 'use your pre-pregnancy size' logic applies here.

Post-surgical and mastectomy bras follow a specialized sizing category entirely

Bras designed for post-surgical recovery or mastectomy needs are sized and constructed around entirely different priorities — soft seams, pocket inserts, gentle compression — than the standard band-and-cup system this chart covers, so converting a regular size into this specialized category isn't appropriate; a specialist retailer's own fitting guidance is the right resource instead.

Strapless and convertible styles trade some precision for versatility

A strapless or convertible bra relies more heavily on band tension to stay in place than a traditional strapped style does, since it can't rely on shoulder straps for support — this makes a snug, accurately converted band size more important for these specific styles than for a standard everyday bra, where straps provide a bit more margin for error.

Multiway and convertible straps add their own separate fit variable

A bra designed to be worn multiple ways — halter, crossback, strapless — relies on the straps for a meaningfully different share of the support than a standard style does, so the band-and-cup conversion this chart covers still applies, but expect to experiment with strap configuration more than with a standard everyday bra at the same converted size.

Padded and push-up styles add internal volume of their own, which is worth remembering when comparing the felt fit against an unpadded style at the identical converted band-and-cup number — the size conversion holds, but the two styles won’t sit identically even so.

Machine washing degrades a bra's band elastic faster than hand washing does

The heat and agitation of a washing machine, even on a gentle cycle, wears down a bra's band elastic measurably faster than hand washing in cool water does, so a bra that's been machine washed weekly for a year can measure smaller in its effective band recovery than an identically aged, hand-washed bra of the same size — worth factoring in before assuming a converted size has simply stopped fitting rather than considering the wash routine.

Significant weight change affects band and cup independently, not proportionally

A meaningful weight gain or loss tends to change band size less than it changes cup volume, since the ribcage itself is largely bone rather than fat tissue, so someone who has gained or lost a noticeable amount of weight often needs to re-check cup size specifically rather than assuming the whole bra size has shifted by the same proportion.

A first-time underwire wearer often needs a slightly different size than a wire-free preference suggests

Someone new to underwire bras, moving over from wire-free styles, sometimes chooses a size based on a wire-free comfort preference that doesn't translate directly, since a structured wire cup fits closer to the body than a soft-cup style does at a nominally identical band and cup number — trying a size that feels slightly snugger than expected on a first underwire purchase is common and not necessarily a sign the conversion was wrong.