Bra Size Calculator US/UK/EU/AU

Answer “what is my bra size?” in seconds: enter two measurements and get your size in US, UK, European, Australian and French sizing, with sister sizes included.

How to Use This Bra Size Calculator

1. Pick your unit. Use inches or switch to centimetres. This works as a bra size calculator cm tool too, so measure in whichever unit your tape shows.
2. Measure your underbust. Wrap a soft tape firmly and level around your ribcage, directly under your bust, and type the number in the first box.
3. Measure your bust. Wrap the tape loosely over the fullest part of your bust, level across your back, and type that number in the second box.
4. Read your sizes. The bra calculator shows your US size in large type, then your UK, EU, AU and FR equivalents, your band, your cup and the bust-minus-band difference behind the result.
5. Check the sister sizes. If the band feels too tight or too loose in the fitting room, try the sister size shown under your result before you change cup volume.

To convert a size you already own instead, open the Bra Size Converter tab at the top of the tool, pick the system printed on your label, and choose the band and cup. It acts as a UK to US bra size converter, an EU-to-US converter and an AU converter in one place.

Why Use This Bra Size Calculator

• Five systems at once. One measurement gives you US, UK, European, Australian and French bra sizes together, so you can shop international brands without a separate conversion chart.
• Inches and centimetres. The tool accepts both units and shows the conversion it used, which makes it a true bra size calculator cm option as well.
• Sister sizes included. Most calculators stop at one size. This one also shows the two neighbouring sizes that hold the same cup volume, which solves most band-fit problems.
• A converter, not just a calculator. Already know your size in one country? Convert it directly instead of re-measuring.
• Free, private and instant. Everything runs in your browser. No sign-up, no cost and no measurement ever leaves your device.
• Built on the standard method. The logic follows the method fitters and size charts use worldwide: band from the underbust, cup from the bust-minus-band difference, with conversions aligned to the EN 13402 band steps used in Europe.

Who Is This Bra Size Calculator For

Bra Size Calculator

A bra size calculator estimates your bra size from two body measurements: the underbust, which sets the band, and the bust, which sets the cup together with the band. Fit matters far beyond comfort. The band provides most of a bra’s support, so a well-fitted bra improves posture, reduces shoulder and neck strain from straps doing work they should not do, and makes clothes sit the way the designer cut them. A poorly fitted bra does the opposite: it digs, rides, gaps and shifts all day.

Fitting studies and retailer surveys regularly estimate that a large share of women wear the wrong size, and the most common error is a band that is too large paired with cups that are too small. Two habits cause most of it. People keep the size they were given years ago even though bodies change, and they trust the letter on the label as if a C cup were a fixed volume. It is not. Cup volume grows with the band, so a 32C, a 34C and a 38C hold three different amounts. That single fact explains why a proper bra calculator always works from measurements, never from your old label.

This calculator uses the snug underbust method that most modern fitters and size charts follow. It rounds your underbust to the nearest even band number, subtracts that band from your bust measurement, and turns the difference into a cup letter: under an inch is AA, then each extra inch steps up one cup. It then converts that one result into five sizing systems at once, because bra sizes are a local language: the same body wears a 34 in New York, a 34 in London, a 75 in Berlin, a 12 in Sydney and a 90 in Paris.

Use the result as your starting size, not a guarantee. Brands grade their patterns slightly differently, cup shapes suit different breast shapes, and stretch changes how a band feels. The sections below teach you to measure well, convert any size, read the full charts, use sister sizes, and run a five-point fit check, so you can land on the size that actually fits your body.

Bra Size Converter

The converter tab at the top of this page turns a size you already know into every other system. Pick the system printed on your current label, choose the band and cup, and read the equivalents instantly. Shoppers use it most often as a UK to US bra size converter when ordering American brands, and in reverse when a UK brand like Panache, Freya or Curvy Kate catches their eye. It also converts European bra sizes to US, French and Spanish sizes, and Australian sizes, which follow UK cup letters on dress-size bands.

Bra Size

A bra size pairs a number with a letter, and each part carries its own meaning. The number is the band: the length of the band that wraps your ribcage, written as inches in the US and UK, as centimetres in Europe, and as a dress size in Australia and New Zealand. The letter is the cup: a code for the difference between your bust and your band, not a fixed volume. Because the cup letter only describes a difference, the same letter on a bigger band holds more. Keep that in mind and the whole system, including sister sizes, suddenly makes sense.

Bra Size Conversion Chart

The chart below shows equivalent bra sizes for a C cup across every band. Tap any row to load that size into the converter at the top of the page, then change the cup to your own letter. The band columns stay identical for every cup; only the cup letter changes as you move through the cup conversion table further down.

Reading the chart is simple. Find the band you wear in your home system, then read across. A US 36, for example, is a UK 36, an EU 80, an AU 14 and an FR 95, whatever the cup letter. Add your own cup using the cup ladder below and you hold a complete international conversion.

Bra Cup Conversion

Cup letters agree across the world up to D, then the systems split, which is why letter-for-letter guessing fails exactly where many shoppers need it most. The US introduces DD and then DDD before moving to single letters G, H, I and beyond. The UK uses DD, then E, F and double letters FF, GG and HH. Europe keeps a clean single-letter ladder with E, F, G and H. Australia follows the UK ladder. This table keys every cup to the measurement behind it, the bust-minus-band difference, so you can convert any cup with confidence.

Two conversions catch people out. A US DDD is not a UK DDD, a label the UK does not use at that step; it is a UK E and an EU F. And a UK FF, GG or HH has no double letter in the US at all; those cups become US H, J and L. When in doubt, convert by the difference row, never by the letter alone. As a cup size calculator check, you can also work backwards: find your letter in your home column, read the difference, then read across to the system you are buying.

Bra Band Conversion

Band conversion is pure arithmetic, and bands convert exactly even when cups do not. US and UK bands are identical numbers. European bands state the underbust in centimetres and step by five: add nothing and guess nothing, just use the table. French, Spanish and Belgian bands add 15 to the European number. Australian and New Zealand bands use dress sizes, which run 22 below the US number. Italian bands, when you meet them, run as small single digits that map to the same rows.

If you need a quick mental conversion away from the chart, multiply a US band by 2.54 and round to the nearest five to land close to the European band: 34 times 2.54 is about 86, which the chart refines to the standard 75 step for a snug underbust in the 73 to 77 cm range. The chart always wins over the shortcut, because brands cut to the chart.

Bust Girth Measurements

Every bra size starts with bust girth measurements, the two circumferences this calculator asks for. The underbust girth runs around the ribcage in the groove directly under the breasts, where the band will sit. The full bust girth runs around the widest point of the chest, usually across the nipple line, with the tape passing over the shoulder blades at the back. Some fitting systems also record a third girth, the overbust above the breasts, which helps with very full or very shallow shapes, but the standard two-girth method on this page covers the great majority of fittings.

Accuracy decides everything downstream. A quarter inch of tape error can shift a cup, and a tilted tape quietly adds length that is not really there. Keep the tape level all the way around, snug without digging in for the underbust, and relaxed without sagging for the bust. Measure at the end of a normal breath out, standing straight with your arms down. Round a fraction up rather than down when you note the numbers, and if your two attempts disagree, measure a third time and use the middle value.

Taking Measurements for Correct Bra Size

1. Wear the right base. Measure braless or in a thin, non-padded bra. Padding and moulded cups add girth that belongs to the bra, not to you.
2. Stand in front of a mirror. The mirror lets you check that the tape stays level across your back instead of sliding up between your shoulders.
3. Take the underbust firmly. Wrap the tape directly under your bust, pull it snug, and breathe out before you read it. This girth sets the band, and the band does the supporting, so it must reflect your ribcage, not your breathing.
4. Take the bust loosely. Wrap the tape over the fullest part of your bust without compressing tissue. It should touch all the way around and slide slightly if you tug it.
5. Write both numbers down. Record inches and centimetres if your tape shows both; the calculator accepts either, and a cm record protects you when you shop European brands later.

No tape? A strip of ribbon or string marked against a ruler works in a pinch, and a standard bank card, at about 3.37 inches (8.56 cm) on its long edge, can stand in as a rough unit. The string method loses precision, so treat its result as an estimate and confirm with a real tape before you spend on several bras.

How to Calculate Bra Size

The full method fits on an index card, and knowing it means you never depend on any single calculator, this one included.

1. Find the band. Round your underbust in inches to the nearest even number. An underbust of 31 becomes a 32 band; 33 becomes 34. In centimetres, the same step lands on the European chart: about 73 to 77 cm wears a 75 band.
2. Find the difference. Subtract the band from your bust measurement. A 36-inch bust on a 32 band gives a 4-inch difference.
3. Turn the difference into a cup. Read the cup ladder: less than 1 inch is AA, 1 is A, 2 is B, 3 is C, 4 is D, 5 is DD, and each further inch steps one cup higher in your system’s ladder.
4. Convert if you need to. Keep the band row from the band chart, then take the cup from the same difference row in the cup chart for the system you are buying.

Worked example. Underbust 33 inches, bust 40 inches. The band rounds to 34. The difference is 40 minus 34, which is 6 inches. Six inches is a US DDD, a UK E, an EU F and an AU E, so the starting sizes are US 34DDD, UK 34E, EU 75F and AU 12E. Notice how one body legitimately owns four different labels, which is the entire reason converters exist.

A note on the underbust +4 method. Some manufacturers still size bands the older way, adding four or five inches to the underbust before naming the band, so the same body can be offered a band two steps larger with a smaller cup letter. This calculator follows the modern snug method, where the band matches the rounded underbust, because most current fitters and charts start there. If a specific brand’s own chart states the +4 method, follow that brand’s chart for that purchase and use your sister sizes to translate between the two.

Sister Sizes

Sister sizes are sizes on neighbouring bands that hold the same cup volume as your size. Move one band down and one cup up to keep the volume on a firmer band, or one band up and one cup down to keep it on a looser band. The classic family is 34C, 32D and 36B: three labels, one cup volume. Sister sizes rescue fittings when your cups sit perfectly but the band feels wrong, and they rescue shopping when your exact size sells out in a style you love.

The calculator prints your two sister sizes with every result, already converted into US, UK and EU labels, so you can walk into a fitting room with three sizes in hand instead of one. Stay within one step of your calculated size; two steps away, the cup shape and strap placement change enough that the family resemblance fades.

Making Sure Your Bra Fits

A calculated size earns its keep only when the bra passes a fit check on your body. Put the bra on properly first: lean forward, settle into the cups, fasten the band on the loosest hook of a new bra, then stand and adjust the straps. Now run the five checks.

• Band: It sits level all the way around, firm enough that only two fingers slide under it, and it stays put when you raise your arms. The band, not the straps, should carry most of the support.
• Cups: Tissue fills the cups smoothly with no spilling at the top or sides and no empty gaping when you lean forward.
• Centre gore: On wired styles, the panel between the cups rests close to your sternum. A gore floating away from the chest usually signals cups that are too small or the wrong shape.
• Straps: They stay on your shoulders without digging. If you need them drum-tight to feel supported, the band is doing too little.
• Underwires: Wires trace the natural curve under each breast and end toward your armpit without poking tissue at either end.

Finish by pulling a fitted top over the bra. The silhouette should look smooth, with no ridges from cup edges and no bulges above the band at the back.

Wrong Bra Signs

Your body reports a wrong size clearly once you know the signals. Treat any of these wrong bra signs as a prompt to re-measure and run the calculator again.

• The band rides up your back. The band is too loose to support you. Go down a band and up a cup: a 36C becomes a 34D.
• You spill over the cups. Quadruple-breast overflow at the top or sides means the cup is too small. Step the cup up before you touch the band.
• The cups gape or wrinkle. The cup is too big or the style suits a fuller shape than yours. Try a cup down or a different cup shape.
• Straps dig into your shoulders. Your straps are compensating for a loose band. A firmer band with the right sister cup usually ends the digging.
• Red marks and poking wires. Marks that fade in minutes are normal; pain, bruising or a wire sitting on tissue is not. Recheck cup size and wire width.
• The gore floats and the centre lifts. The cups lack the depth you need. Try a cup size up in the same band.
• Back, neck or shoulder pain. Persistent pain alongside other signs points to support failing. Re-measure, refit, and consider a professional fitting for high-impact needs.

Bras for Special Tasks

One size serves every bra you own, but each job asks for a different design. Use your calculated size as the entry point, then choose the build that matches the task.

44 DDD Bra Size Equivalent

Shoppers search for the 44 DDD bra size equivalent because DDD is where the US ladder leaves the shared letters behind, and a 44 band sits at the wide end of most charts. Here is the full conversion, ready to copy: a US 44DDD equals a UK 44E, a European 100F, a French, Spanish or Belgian 115F, and an Australian 22E. Its sister sizes are 42G in US terms if you want a firmer band at the same cup volume, and 46DD if you want a looser one. Run the same conversion for any size in the converter tab: pick US, band 44, cup DDD, and every equivalent appears with its sister sizes.

What Is a Double G Bra Size?

A double G bra size is written GG on the label. It belongs to the UK and Australian ladders, where double letters mark half-steps in the larger cups: after FF comes G, then GG, then H, then HH. GG is a single cup size, one step above G; it does not mean two G cups sewn together, and it holds only slightly more than a G on the same band. A UK 34GG converts to a US 34J, a European 75J and stays a 12GG in Australia, because Australia shares the UK ladder. American brands print no GG at all, so a shopper moving from a UK brand to a US brand must convert by the difference row in the cup chart, where GG sits at a 10-inch difference.

Work Out Your Bra Size UK: The Free Online Route

To work out bra size UK style, measure exactly as above, then read the UK column of your result. UK bands match US bands number for number, and UK cups match the US up to DD, then run E, F, FF, G, GG and H where the US runs DDD, G, H, I, J and K. Many shoppers type “free online bra size calculator uk nhs” into Google while hunting for a trustworthy, no-cost tool. Bra fitting is a clothing service rather than a clinical one, so there is no official NHS bra calculator to find; a free independent calculator like this one, built on the standard measuring method and the published UK size ladder, does the same job in the same way a high-street fitter would start.

Bra Size Calculator in CM

Most of the world measures in centimetres, so this page works as a full bra size calculator cm tool: tap the centimetres toggle, type your underbust and bust in cm, and the result arrives in all five systems. Behind the toggle, the calculator divides by 2.54 to work in inches, because the cup ladder is defined in inch steps, then converts the band onto the European centimetre chart at the same time. Two reference points anchor the scale: a US and UK 34 band is the same band as an EU 75 and an AU 12 on the conversion chart, and a bust-minus-band difference of about 2.5 cm equals one cup step. If your tape reads 86 cm underbust and 95 cm bust, expect a US 34C, a UK 34C, an EU 75C and an AU 12C, and let the tool confirm it.

A Bra That Fits Calculator vs This Calculator

Readers of the well-known Reddit community often arrive from the a bra that fits calculator, which takes six measurements, including leaning and lying bust girths, and models breast shape more deeply. That depth helps people with projected, shallow or very full shapes fine-tune a starting size. This calculator takes the classic two-measurement route that retailer charts, the EN 13402 band steps and most professional first fittings share, and spends its extra effort where the six-measurement tool does not: instant conversion across US, UK, EU, AU and FR labels, full published charts, and sister sizes on every result. Use this page to find and convert your size fast; if your shape is hard to fit and a style keeps failing in one spot, the deeper measurement set is a good second opinion, and the two results usually agree within one sister step.

Frequently Asked Questions

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