Bra Size Calculator
Turn your underbust and bust measurements into a starting band and cup size, with US, UK, EU, French, Australian and Japanese labels and sister sizes.
Band method and leaning bust (optional)
Your measurements stay in this browser. Nothing is sent or stored.
Band 32 from a 31 in underbust; a 4 in difference gives a D cup.
A starting size to try on. Brands and styles fit differently, so check the fit with the list below.
Your size in other countries
| UK | EU | FR / ES | AU / NZ | JP |
|---|---|---|---|---|
| 32D | 70D | 85D | 10D | 70E |
Label equivalents from Wacoal's international size guide. Brands differ: some US brands label DD as E and DDD as F, and French labels have changed over time.
Your calculation
The same steps the calculator runs, with your numbers.
- Band, modern method: 31 rounded to the nearest even number = band 32.
- Difference: 36 โ 32 = 4 in, rounded to 4 cup steps.
- Cup: step 4 is D in US letters.
- Labels abroad: US band 32 = EU 70 (2.5 ร 32 โ 10) = FR 85 = AU 10.
Bust measurement by band and cup
Each cell is the bust measurement in inches for that size with a modern band. Your size is filled in and the two nearest sister sizes are outlined.
| Band (underbust in) | A | B | C | D | DD | DDD | G |
|---|---|---|---|---|---|---|---|
| 28 (27โ29) | 29 | 30 | 31 | 32 | 33 | 34 | 35 |
| 30 (29โ31) | 31 | 32 | 33 | 34 | 35 | 36 | 37 |
| 32 (31โ33) | 33 | 34 | 35 | 36 | 37 | 38 | 39 |
| 34 (33โ35) | 35 | 36 | 37 | 38 | 39 | 40 | 41 |
| 36 (35โ37) | 37 | 38 | 39 | 40 | 41 | 42 | 43 |
Fit check when you try it on
- Band: level all the way around and firm on the loosest hook, with room for about two fingers underneath. A band that rides up at the back is too big.
- Cups: no spilling over the top or sides and no gaping or loose fabric.
- Center: the center front (gore) lies flat against the breastbone.
- Underwire: sits flat on the ribcage around the breast, not on breast tissue.
- Straps: stay in place without digging in. The band, not the straps, carries most of the support.
A starting estimate from two measurements. Bra sizing is not standardized across brands or countries, so the size that fits can differ by a band or cup.
How the Bra Size Calculator Works
This bra size calculator turns two tape measurements, the underbust and the bust, into a starting band and cup size. The band comes from the underbust. The cup comes from how much larger the bust is than the band, at one cup letter per inch. The calculator then converts that size to the labels used in the UK, US, Europe, France and Spain, Australia and New Zealand, and Japan, and shows sister sizes and a chart of nearby sizes.
Bra sizes are not standardized between brands. A 34C from one maker can fit differently from a 34C by another, and a plunge style fits differently from a full cup. Treat the result as the size to try first, then use the fit check to move up or down.
When you enter centimeters, the calculator divides by 2.54 first, because US and UK sizes are defined in inches. Half an inch rounds up: an underbust of 31 inches gives band 32, and a 4.5 inch difference gives a DD. A measurement that close to an odd inch can fall either way, so 78.7 cm (30.98 in) gives band 30 while 78.74 cm (exactly 31 in) gives band 32; try both bands in that case.
How to Measure Your Bra Size
You need a soft tape measure and a mirror. Wear an unpadded bra that fits reasonably, or no bra, because padding adds to the bust measurement and changes the cup.
- Underbust. Wrap the tape around your ribcage directly under the breasts, where a bra band sits. Keep it level all the way around, snug but not digging in, and read it after breathing out normally.
- Bust. Stand straight with arms relaxed and measure around the fullest part of the bust. Keep the tape level across the back and loose enough that it does not press into breast tissue.
- Leaning bust (optional). Bend forward at the waist until your back is roughly level and measure the fullest part again. Some fitters use it as a second reading for the cup. The calculator averages the two when you fill it in.
- Repeat. Take each measurement two or three times and use the average.
Breathing changes the numbers. In McGhee and Steele's 2006 study, measuring after a full breath in made the underbust larger by an average of 1.9 inches, enough to move the band by about one size. They recommended measuring at relaxed breath out, and they took each measurement three times and used the mean.
Measuring without a tape: the string method
Wrap a piece of string, ribbon or a phone charger cable around the same places, pinch or mark the point where it overlaps, then lay it flat along a ruler or a carpenter's tape. If you measure in centimeters, divide by 2.54 for inches, or switch the calculator to centimeters.
When to measure again
Measure again after a change in weight, during and after pregnancy, while nursing, after breast surgery, or when bras that used to fit start to ride up or gape. Measurements can also vary over a menstrual cycle: Wood and colleagues found a moderate correlation between cycle stage and bra fit in their 2008 study of 30 women.
Band Size and Cup Size Formulas: Modern vs Plus 4 Method
Two methods are in common use, and they give different sizes for the same person. The calculator uses the modern method by default and lets you switch under Band method.
Modern method
Plus 4 method
The plus 4 method still appears in printed guides, including the bra fitting guide from the UK charity Breast Cancer Now, which also notes that sizes vary by brand and style. Researchers have questioned the added inches. McGhee and Steele measured 16 women with larger busts and found that sizes calculated with 4 or 5 inches added matched the bras the women wore, within one band and cup size, for only 4 of them when measured on the exhale. The authors recommended the raw underbust, without arbitrary additions, for the band.
The two methods differ most for a large bust to underbust difference. For a 32 inch underbust and 38 inch bust, plus 4 gives 36B while the modern method gives 32DDD in US letters (32E in UK letters). The sister sizes of 32DDD are 34DD and 36D, so the plus 4 result has a looser band and two fewer cup steps of volume at the same band.
Bra Size Chart: Cup Letters by Difference
Each inch of difference between the bust and the band is one cup step. The letters match up to D and then split, because the UK uses double letters (DD, FF, GG) and Europe uses single letters. US brands vary most after DD.
| Bust โ band | US | UK and AU | EU and FR | Japan |
|---|---|---|---|---|
| 0 in | AA | AA | AA | A |
| 1 in | A | A | A | B |
| 2 in | B | B | B | C |
| 3 in | C | C | C | D |
| 4 in | D | D | D | E |
| 5 in | DD (or E) | DD | E | F |
| 6 in | DDD (or F) | E | F | G |
| 7 in | G | F | G | H |
| 8 in | H | FF | H | I |
| 9 in | I | G | I | J |
| 10 in | J | GG | J | K |
| 11 in | K | H | K | Not listed |
| 12 in | L | HH | L | Not listed |
| 13 in | M | J | M | Not listed |
| 14 in | N | JJ | N | Not listed |
| 15 in | O | K | O | Not listed |
The US and UK sequences follow Wacoal Canada's chart for Elomi, Freya and Fantasie, which runs from US AA to O alongside UK AA to K. The EU, French, Australian and Japanese letters follow Wacoal's international size guide, which lists Japanese cups one letter above UK cups up to UK GG. Some retailers print US DD as DD/E and DDD as DDD/F.
US vs UK vs EU Bra Sizes and International Conversion
US and UK bands use the same numbers. Europe and Japan label the band in centimeter steps of 5, France and Spain add 15 to the European number, and Australia and New Zealand subtract 22 from the UK number. The underbust columns show which measurements give each band with each method.
| US / UK | EU / JP | FR / ES | AU / NZ | Underbust, modern | Underbust, plus 4 |
|---|---|---|---|---|---|
| 30 | 65 | 80 | 8 | 29 to 31 in | 25 to 26 in |
| 32 | 70 | 85 | 10 | 31 to 33 in | 27 to 28 in |
| 34 | 75 | 90 | 12 | 33 to 35 in | 29 to 30 in |
| 36 | 80 | 95 | 14 | 35 to 37 in | 31 to 32 in |
| 38 | 85 | 100 | 16 | 37 to 39 in | 33 to 34 in |
| 40 | 90 | 105 | 18 | 39 to 41 in | 35 to 36 in |
| 42 | 95 | 110 | 20 | 41 to 43 in | 37 to 38 in |
| 44 | 100 | 115 | 22 | 43 to 45 in | 39 to 40 in |
| 46 | 105 | 120 | 24 | 45 to 47 in | 41 to 42 in |
The band labels come from Wacoal's chart for UK 30 to 46. Outside that range the calculator continues the same steps, so UK 28 is EU 60, FR 75 and AU 6. With the modern method a measurement that lands exactly on an odd number rounds up, so 31 inches is band 32.
The EN 13402 measured size
The European standard EN 13402 labels bras directly from body measurements in centimeters. Table A.9 of EN 13402-3:2017 sets the band at the underbust rounded to the nearest 5 cm (60, 65, 70 up to 125) and the cup from the bust minus the underbust in 2 cm steps.
| EN 13402 cup | AA | A | B | C | D | E | F | G | H |
|---|---|---|---|---|---|---|---|---|---|
| Bust โ underbust (cm) | 10 to 12 | 12 to 14 | 14 to 16 | 16 to 18 | 18 to 20 | 20 to 22 | 22 to 24 | 24 to 26 | 26 to 28 |
The standard's own example, an 89 cm underbust and a 108 cm bust, gives a 19 cm difference and a 90D. The modern method gives the same body a 36 band (35.04 inches) and a 7 inch difference, UK 36F, which converts to EU 80G. A difference of exactly 16 cm counts as C here, as in the C&A guide, where a 76 cm underbust and 92 cm bust give 75C.
's chart asks for underbust and bust in centimeters, start from the EN 13402 size for that brand. If it lists UK or US sizes, start from the calculator's main result.Sister Sizes Explained
A cup letter is not a fixed volume. The cup on a 36B holds about as much as the cup on a 34C or a 32D, because a longer band carries a wider cup. Bras along that diagonal are sister sizes.
one band up and one cup down keeps the volume similar and loosens the band. Moving one band down and one cup up tightens it.| Sister of 34C | 30DD | 32D | 34C | 36B | 38A |
|---|---|---|---|---|---|
| EU label | 65E | 70D | 75C | 80B | 85A |
| Bust at that size | 35 in | 36 in | 37 in | 38 in | 39 in |
Sister sizes help when only one part of the bra is wrong. If the cups fit but the band rides up even on the tightest hook, go down a band and up a cup. If the band feels tight on the loosest hook while the cups fit, go up a band and down a cup. Sister sizes more than one step away fit less predictably, because the wire width and strap position change with the band.
How Should a Bra Fit?
Elomi's fitting guide checks five points, and the calculator's fit list covers the same points.
- Center front. The gore between the cups sits flat against the breastbone. If it lifts away, the cups are often too small.
- Band. Firm and level with the underwire. You can slide two fingers under it but cannot pull it more than about two inches from the body. A band riding up at the back is too big. Fasten a new bra on the loosest hook so the tighter hooks are available as the elastic relaxes.
- Cups. They enclose the breast with no overspill at the top or sides and no gaping. Spilling means go up a cup; loose fabric means go down one.
- Straps. Comfortable and firm without leaving marks. McGhee and Steele note that a band that is too loose makes the straps bear extra pressure.
- Underwire. Lies flat against the chest. A wire that sits away from the chest or digs in at the sides points to cups that are too small.
Measuring is only part of the process. McGhee and Steele's 2010 study of 104 women found that 85 percent were wearing bras that did not meet professional fitting criteria, and that sizes from self selection or measurement systems differed significantly from the professionally fitted size. Wood and colleagues found 80 percent of the 30 young women in their study wore an incorrectly sized bra: 70 percent wore bras that were too small and 10 percent bras that were too large, judged against Triumph International fitting criteria.
How to Use the Calculator
- Units. Pick inches or centimeters. Switching converts the values already entered.
- Size system. Choose whether the main result uses US or UK cup letters.
- Underbust and bust. Enter both measurements as described above.
- Options. Switch to the plus 4 method or add a leaning bust measurement.
- Read the result. Start with the main size, then check the conversions, sister sizes and chart.
Common Mistakes
- Measuring over a padded bra. Padding adds to the bust and inflates the cup.
- Pulling the bust tape tight. It lowers the bust and the cup letter.
- Measuring after a deep breath. It enlarges the underbust.
- Mixing systems. A UK E is a US DDD and an EU F.
- Judging cups alone. A tighter band with a bigger cup letter can hold the same volume.
Worked Examples
Metric measurements: 75 cm underbust, 92 cm bust
This is a common case where the two European approaches disagree, and the reason the calculator shows both.
Small band: 28 in underbust, 34 in bust
Plus 4 would give 32B for the same measurements. Fewer brands make 28 and 26 bands, so specialist brands are often the place to look.
Larger band: 38 in underbust, 44 in bust
Small difference: 34 in underbust, 35 in bust
When the plus 4 method falls below AA, the calculator says so instead of inventing a cup letter.
Frequently Asked Questions
How do I measure my bra size at home?
Wear an unpadded bra or no bra and use a soft tape to measure the underbust snugly around the ribcage just below the breasts, keeping the tape level and breathing out. Then measure the bust loosely around the fullest part while standing straight. With the modern method, round the underbust to the nearest even inch for the band, subtract the band from the bust and count one cup per inch. An underbust of 31 inches and a bust of 36 inches gives a 32 band, a 4 inch difference and a 32D starting size.
What does 34C mean in bra size?
The number is the band size and the letter is the cup size. With the modern method a 34 band suits an underbust from about 33 to 35 inches, and a C cup means the bust is about 3 inches larger than the band, so a 34C usually matches a bust of about 37 inches. The same label is 75C in Europe, 90C in France and 12C in Australia. A C cup is not a fixed volume: 32D and 36B hold about the same cup volume as 34C, which is why they are called sister sizes.
Is DD the same as E in bra sizes?
Not in UK sizing: a UK DD is the fifth cup step, one above D, and a UK E is the sixth step, a 6 inch difference. In US sizing the fifth cup is usually DD, some brands label it E, and the sixth cup is DDD or F. European labels skip double letters, so UK DD equals EU E and UK E equals EU F; Wacoal's international chart lists UK 34DD as EU 75E and US 34DD, and UK 34E as EU 75F and US 34DDD. Check which system a label uses before comparing letters.
What are sister sizes in bras?
Sister sizes are bra sizes with about the same cup volume on a different band: go one band size up and one cup down, or one band down and one cup up. The nearest sisters of 34C are 32D and 36B, and the next ones out are 30DD and 38A. Use a sister size when the cups fit but the band does not: if a 34C band rides up at the back, try 32D, and if it feels tight on the loosest hook, try 36B. The calculator shows the two nearest sister sizes for your result.
Should I add 4 inches to my band size?
The plus 4 method adds 4 inches to an even underbust, or 5 to an odd one, and some guides still print it. It gives a larger band and a smaller cup letter than the modern method. In a study of 16 women with larger busts, McGhee and Steele (2006) found that sizes from this method matched the bras the women wore, within one band and cup size, for only 4 of them when measured on the exhale, and they recommended using the raw underbust. For a 31 inch underbust and 36 inch bust, plus 4 gives 36AA and the modern method gives 32D.
How do I convert a UK bra size to EU?
Convert the band and the cup separately: UK bands 30, 32, 34, 36 and 38 become EU 65, 70, 75, 80 and 85, so the EU band is 2.5 times the UK band minus 10. France and Spain add 15 to the EU band, and Australia subtracts 22 from the UK band. Cups match up to D; after that, EU labels skip double letters, so UK DD is EU E, UK E is EU F, UK F is EU G and UK FF is EU H. A UK 32DD is EU 70E and FR 85E.
Sources & References
- European Committee for Standardization (CEN). EN 13402-3:2017, Size designation of clothes, Part 3: Size labelling based on body measurements and intervals, Table A.9 (bras: underbust in 5 cm steps, cups AA 10 to 12 cm through H 26 to 28 cm). Catalog entry: standards.iteh.ai
- International Organization for Standardization. ISO 4416:1981, Size designation of clothes: Women's and girls' underwear, nightwear, foundation garments and shirts (withdrawn; replaced by ISO 8559-2:2017). iso.org
- Wacoal. International Size Guide (UK, Europe, France, AUS/NZ, USA and Japan band and cup conversions). wacoallingerie.com
- Wacoal Canada. Size Charts (US cups AA to O beside UK cups AA to K for Elomi, Freya and Fantasie). wacoal.ca
- Wacoal Europe. Global Sizing Guide (UK and US sizing and the change to French cup labels). Wacoal Europe
- Affair Lingerie. Panache size guide (UK to US cup conversion printed as DD/E and DDD/F). affairlingerie.com
- C&A. How to measure bra size (underbust and standing bust in cm, 76 cm and 92 cm giving 75C). C&A
- Elomi. Bra Fitting Guide: How Should a Bra Fit? (five step fit check). elomilingerie.com
- Breast Cancer Now. Your guide to a well fitting bra (plus 4 or 5 band method; sizes vary by brand and style). breastcancernow.org
- McGhee, D. E. and Steele, J. R. How do respiratory state and measurement method affect bra size calculations? British Journal of Sports Medicine, 2006, 40(12), 970 to 974. doi.org/10.1136/bjsm.2005.025171
- McGhee, D. E. and Steele, J. R. Optimising breast support in female patients through correct bra fit: a cross sectional study. Journal of Science and Medicine in Sport, 2010. doi.org/10.1016/j.jsams.2010.03.003
- Wood, K., Cameron, M. and Fitzgerald, K. Breast size, bra fit and thoracic pain in young women: a correlational study. Chiropractic & Osteopathy (now Chiropractic & Manual Therapies), 2008, 16:1. doi.org/10.1186/1746-1340-16-1
Results are a starting estimate from your measurements. Fit varies by brand, style and body shape, so try the size on and use the fit check. Every number on this page was recomputed with the same functions the calculator uses. Methodology reviewed: 2026.