Find your size16 countries, one tape measure
Free bra size calculator · worldwideFind the bra size that actually fits — then read it in any country's labels
A bra size is just two facts written in code: how big your ribcage is, and how much fuller your bust is than that ribcage. Enter both measurements and we'll decode them into US, UK, European, French, Australian, Indian and Japanese sizes, plus the sister sizes worth trying when a style runs small or large.
One body, four labels — each tag above describes the same fit.
Bra size calculator
Pick the country whose labels you shop in.
Snug and level, right under the bust.
Loose, across the fullest point.
Please enter both measurements, with the bust equal to or larger than the underbust.
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One body, sixteen labels
Travelling, moving abroad or ordering from an overseas brand? Here's the same fit as it would read on a tag in each market. It shows a 34C example until you calculate, then switches to your size. Tap a country to use its labels in the calculator.
Japanese and Korean sizes use their own centimetre scale and are approximate. Brands vary inside every country, so check each brand's size chart when you can.
Your size and its sister sizes across six labelling systems
Each row is a size with about the same cup volume as yours. The highlighted row is your calculated fit; the rows around it are the swaps to reach for when a band feels too firm or too loose. Until you calculate, the table shows a 34C as an example.
| Sister step | US | UK / IN | EU / DE | France | Italy | AU / NZ | Underbust |
|---|
Italian bands are numbered rather than measured. Centimetre systems step their cups every 2 cm rather than every inch, so above a D the European letter is an approximation — check the brand's own chart for full-bust styles.
What the number and the letter really mean
Every label you'll find in a shop, whether it says 34C, 75C or 12C, carries the same two pieces of information. Once you know what each half is doing, sizing stops feeling arbitrary.
The band: your ribcage
The number describes the elastic band that wraps your ribcage. It's the band, not the straps, that does most of the lifting — which is why it has to fit firmly.
The cup: the difference
The letter doesn't measure breast size on its own. It records how much bigger your bust is than your band. A C means about three inches of difference, whatever the band.
The band and centre gore anchor the bra, wires frame each breast, cups hold the volume and straps mostly stabilise.
Measure yourself in three minutes
You need a soft tailor's tape and a mirror. Measure over a thin, unlined bra or bare skin — moulded foam adds bulk the tape will faithfully record.
Stand naturally and breathe out
Arms relaxed by your sides. Holding your breath or lifting your shoulders expands the ribcage and inflates the band reading.
Underbust: snug and level
Wrap the tape around your ribcage right where a bra band sits. Check in the mirror that it isn't climbing at the back. Pull firm, not tight — that number, rounded, is your band.
Bust: loose and level
Move the tape to the fullest point, usually across the nipples, and let it rest on the skin without compressing anything.
Lean forward for a second reading
If your breasts are soft or full, or have changed after pregnancy or weight loss, bend forward to 90° and measure again. Average the standing and leaning numbers — leaning captures tissue that gravity hides.
difference = bust − band
1″ A · 2″ B · 3″ C · 4″ D · 5″ DD · 6″ E (UK) / DDD (US)
Keep both loops parallel to the floor and check the back in a mirror. Timing matters too: measure mid-cycle if you have periods, and again after any big change in weight, training, pregnancy or nursing. More in the full measuring guide, or try measuring without a tape.
The cup letter for every inch of difference
Up to DD, US and UK agree letter for letter. After that they branch: the UK introduces doubled letters (FF, GG, HH), most US brands go through DDD and then single letters, and centimetre systems simply walk the alphabet. That's why one bra can carry three different labels.
| Bust − band | US | UK · AU · IN | EU · FR · IT | Japan JIS (own cm scale) |
|---|
Japanese JIS sizing measures the gap directly in centimetres, starting the A cup at about 10 cm and stepping every 2.5 cm. Its column lists that scale alongside, rather than converting letter for letter. Full charts: cup size chart · bra size chart.
Same volume, different band
Because the cup letter is measured against the band, the cup grows with every band step even when the letter stays put. Turn that around and you get sister sizes: go up one band and down one cup (or the reverse) and the cups hold roughly the same amount.
It's the most useful trick in bra shopping, as long as you remember what changes:
- The band changes. A sister up feels looser around the ribs and lifts less; a sister down feels firmer.
- The wires change. Larger sister sizes use wider wires, which can poke under the arm if your breast root is narrow.
- Stay within one step. Two steps away, the band difference is usually too big to give the same support.
Click any cell to light up its sister family. For the complete list use the sister size calculator or sister size chart.
UK cup letters. Each diagonal is one family of similar-volume sizes.
The five-point check that matters more than any number
Fasten a new bra on its loosest hook, lean forward and scoop each breast into its cup from the side, then stand up and check these five points in a mirror — front and side.
Band: firm and level
Two fingers slide under the back, and it stays horizontal when you lift your arms overhead.
Centre gore: touching
The middle panel lies flat against your breastbone. If it floats, the cups are usually too small.
Wires: on the ribcage
They trace the crease where each breast meets the chest and finish behind the tissue at the side, never sitting on it.
Cups: smooth edge to edge
No bulge over the top or sides, and no wrinkles or hollow space at the neckline.
Straps: steady, not straining
They stay put without leaving grooves. If they're doing the lifting, the band is too loose.
If something's off, here's what it usually means
| What you notice | Likely cause | Try |
|---|---|---|
| Band rides up your back | Band too big | Down a band, up a cup |
| Straps dig into shoulders | Loose band, so straps carry the weight | Firmer band, then loosen straps |
| Tissue spills over the cup | Cup too small or too shallow | Up a cup, or fuller coverage |
| Wrinkles or gaps in the cup | Cup too big, or the wrong shape | Down a cup, or a plunge or balconette |
| Centre gore lifts off the chest | Cups too small or wires too narrow | Up a cup; check wire width |
| Wires poke under the arm | Wires too wide or sides too tall | Lower-sided style, or a sister down |
| Band leaves deep red marks | Band too small | Up a band, down a cup |
| Straps keep slipping off | Straps set wide or stretched | Shorten, or try racerback |
More detail in the bra fit guide and signs you're wearing the wrong size.
Why the same bra has a different label in every country
There's no single global standard. Countries share the band-and-cup idea but disagree on the unit for the band, the size of each cup step, and what comes after D. Here's how the main families work.
Inch band, US letters
Band in inches, one cup letter per inch. Past DD most brands use DDD, then G, H, I — though some label the sixth step F instead of DDD.
e.g. 34DDDInch band, UK letters
The same inch bands as the US, but past DD the UK runs E, F, FF, G, GG, H. Most Indian and Singaporean retailers follow this pattern.
e.g. 34EDress-size band, UK letters
Bands are written as dress sizes: subtract 22 from the inch band. A 34 becomes a 12, a 36 a 14.
e.g. 12ECentimetre band, alphabet cups
The band is the underbust in centimetres, in 5 cm steps (a 34 is a 75). Cups follow the alphabet with no doubled letters.
e.g. 75FCentimetre band plus 15
The same European cups, but the band number is 15 higher. A German 75 is sold as a French 90.
e.g. 90FNumbered bands
Italian bands are numbered rather than measured: 1 for a 32, 2 for a 34, 3 for a 36 and so on, with European-style cups.
e.g. 2FAll in centimetres
JIS sizing rounds the band to 5 cm and measures the bust-to-band gap in centimetres, starting the A cup at about 10 cm and stepping every 2.5 cm.
e.g. 75DFollow the label's origin
Many countries have no national standard, so shops use the system their brands were made for. Check where the garment comes from, not where you're standing.
Tip: read the care labelAlready know one size?
Skip the tape and convert straight between systems.
International converter →The right size in the wrong shape still won't fit
Size tells you how much room the cups need; style decides where that room sits. Breasts that are fuller at the bottom, fuller on top, close-set or wide-set suit different cuts. Use this as a starting map, then try the breast shape quiz.
T-shirt / contour
Seamless foam cups that hold their own shape and disappear under fitted tops.
Suits: even fullness, smooth-look outfitsBalconette
Lower, wider-set cups with straps near the edges, lifting from underneath.
Suits: fuller lower half, wider-set breastsPlunge
A deep, low centre gore that brings the breasts closer together.
Suits: close-set or shallow shapes, low necklinesFull cup
Tall cups that enclose all of the tissue, often with side support panels.
Suits: full on top, projected or larger cupsWire-free & bralette
Shaped by seams and fabric rather than wires; soft and flexible.
Suits: comfort days, smaller cups, sensitive skinSports
Encapsulation (separate cups) or compression (held against the chest), rated by impact level.
Suits: match it to the activity — sports bra calculatorMinimiser
Redistributes tissue to reduce forward projection, often by around an inch.
Suits: button-front shirts, very projected shapesLongline
An extended band reaching toward the waist that spreads pressure over more skin.
Suits: extra anchoring, strapless wearNursing & maternity
Stretchy cups and drop-down clips that allow for daily size swings.
Suits: pregnancy and feeding — nursing sizingYour size isn't fixed — expect it to move
Most people change size several times as adults. The measuring method stays the same; what changes is how often to repeat it and which styles make the transition comfortable.
As a rule of thumb, re-measure once or twice a year, and any time a bra that used to fit starts riding up, gaping or digging in. The life-stage calculators adapt the method for each phase.
First bras
Soft-cup and wire-free styles adapt as size changes quickly. Re-check every few months rather than once a year.
Cycle changes
Many people feel fuller before a period. Measure mid-cycle, and keep a stretch-lace or soft bra for fuller days.
Band and cup both grow
Cups often grow from early on and the ribcage widens later. Choose comfort and room on the hooks.
Daily swings
Size can shift between feeds. Flexible cups and a size taken late in pregnancy are a sensible starting point.
Both measurements move
Weight change affects bust and band; strength training can broaden the back. Re-measure rather than guessing.
Softer tissue, new shape
Tissue often becomes softer and fuller at the bottom. Use the leaning measurement and try balconette or full-cup shapes.
Six sizing beliefs worth letting go of
Make a well-fitting bra keep fitting
The elastic in the band wears out first, and heat is its worst enemy. A few habits go a long way toward stretching the useful life of every bra.
Start new bras on the loosest hook and move inward as the band relaxes over the months.
Elastic recovers when it rests for a day between wears.
Hand wash, or use a mesh bag on a cool, gentle cycle. Fasten the hooks first so they don't snag.
Air-dry flat or hang by the centre gore. Dryer heat breaks down elastane fibres.
When to replace: if the band rides up even on the tightest hook, the wires have bent or started poking through, or the cups have creased for good, the bra has stopped doing its job. With a rotation, everyday bras typically last six to twelve months.
Fitting terms, in plain words
- Band
- The elastic base circling the ribcage; it does most of the supporting.
- Centre gore
- The small panel between the cups that should rest on the breastbone.
- Wings
- The side and back sections of the band, running from the cups to the hooks.
- Underwire
- The U-shaped wire under each cup that frames the breast.
- Breast root
- The footprint where breast tissue meets the chest; it decides the wire width you need.
- Projection
- How far the breasts extend forward from the chest. Projected shapes need deeper cups.
- Sister size
- A size with similar cup volume on a band one step up or down.
- Scoop and swoop
- Leaning forward and gathering tissue from the side into the cup after putting a bra on.
- Spillage
- Tissue bulging over the top or side of a cup — a sign it's too small or shallow.
- Gaping
- Empty space at the top of a cup — usually too big a cup or the wrong shape.
- Encapsulation
- A sports bra design with a separate cup for each breast, rather than pressing both flat.
- JIS
- Japanese Industrial Standard — Japan's centimetre-based clothing size system.
Prefer to watch? See the tape in action
A short walkthrough of both measurements, including where the tape tends to slip. Watch it once, then measure along with it and drop your numbers into the calculator above.
Frequently asked questions
Quick answers to what people ask most. The full FAQ page has many more, with search.
Go deeper with a dedicated calculator or chart
Sizing
Bra size full calculator Sister sizes every swap Cup size letter only Band size one tape Bust only quick estimate Size → bust reverseLife stage & activity
Teen & first bra gentle start Pregnancy by trimester Nursing flexible fit Postpartum after birth Plus size 38+ bands Sports bra by impactShort reads for specific fit problems
Why does my bra ride up?
The four usual culprits and how to tell them apart.
Read → ChecklistSigns you're in the wrong size
What gaps, marks and spillage are telling you.
Read → ExplainerCup size vs breast size
Why one letter can mean very different volumes.
Read → How-toNo tape measure?
Two workarounds using things you already own.
Read →