Bra Size Calculator

Find your starting bra size from two measurements, in EU, FR/ES, IT, UK, US or AU sizes, with sister sizes and the size a store chart would give.

Measure Convert a size

cm in

Underbust, snug

Bust, standing

Use six measurements (more precise)

Show the size in

Your starting size (US)

32DD

Modern fitting (snug underbust, no +4), as used by r/ABraThatFits

One band up, often more comfortable

34D

The old +4 method gives 36A. The same cups on band 36, 2 bands looser: 36C.

The same size in other systems

EU (Germany, Poland)

70E

FR/ES (France, Spain)

85E

IT (Italy)

UK (Britain, Ireland)

32DD

AU (Australia, NZ)

10DD

Sister sizes

Two bands down, two cups up	28G
One band down, one cup up	30DDD
This size	32DD
One band up, one cup down	34D
Two bands up, two cups down	36C

Sister sizes hold the same cup volume on a different band: one band down, one cup up.

A starting size, not a guarantee: brands and styles cut differently. Try it and its sister sizes, and check the fit below.

How to measure

Wear no bra, or a non-padded one.
Keep the tape level all the way around, in front of a mirror if you can.
Underbust: just under the bust, pull the tape as snug as you’d want a band to feel, breathing normally.
Bust: standing upright, measure loosely around the fullest point.
Measure twice. If the two readings differ, use the average.

Check the fit

The band rides up at the back: go one band down and one cup up.
The center panel lifts away from the chest, or the cups overflow: go one cup up.
The cups gape or wrinkle: go one cup down.
The underwire sits on breast tissue at the sides: go one cup up.
The straps carry most of the weight: go one band down.

Why stores give a different size

Most store charts in continental Europe follow the EN 13402 standard: the underbust is rounded to the nearest 5 cm, and the cup is read from bust minus underbust in 2 cm steps.

In the US and the UK, the traditional method adds 4 or 5 inches to the underbust. Both usually give a band two sizes looser (one to three, depending on the measurement), with smaller cup letters, than modern fitting.

A 2012 study in Ergonomics (White and Scurr) found the traditional method overestimates band size and underestimates cup size. The line under your result shows what a store chart would say, and the same cups on that band.

Band sizes by system

EU	FR/ES	IT	UK/US	AU
60	75	0	28	6
65	80	1	30	8
70	85	2	32	10
75	90	3	34	12
80	95	4	36	14
85	100	5	38	16
90	105	6	40	18
95	110	7	42	20
100	115	8	44	22
105	120	9	46	24
110	125	10	48	26
115	130	11	50	28
120	135	12	52	30
125	140	13	54	32
130	145	14	56	34

UK and US bands are the same. Italian bands are numbers: IT 1 = EU 65, IT 2 = EU 70, IT 3 = EU 75.

Cup sizes by system

EU/FR/ES/IT	UK	US	AU
AA	AA	AA	AA
A	A	A	A
B	B	B	B
C	C	C	C
D	D	D	D
E	DD	DD	DD
F	E	DDD	E
G	F	G	F
H	FF	H	G
I	G	I	H
J	GG	J	UK size
K	H	K	UK size
L	HH	L	UK size
M	J	M	UK size
N	JJ	N	UK size
O	K	O	UK size
P	KK	P	UK size
R	L	UK size	UK size
S	LL	UK size	UK size
T	M	UK size	UK size
U	MM	UK size	UK size

Read across a row: every cell is the same cup. Up to D all systems agree; above it, brands grade cups differently, so check the brand’s own chart. “UK size”: that system has no label for this cup, and brands that make it use UK sizes.

Updated: November 3, 2026

Bra size calculator. Band, cup and sister sizes from two measurements.

This bra size calculator turns a snug underbust and a bust measurement into a starting band and cup, with no 4 inches added to the band. It follows the r/ABraThatFits method, gives that size in US, UK, EU, FR/ES, IT and AU labels with its sister sizes, and prints what an old +4 or EN 13402 store chart would give for the same tape readings.

What a bra size measures, and why calculators disagree

A bra size has two parts: a band number for the circumference of the ribcage under the bust, and a cup letter for how much larger the bust is than that band. In US and UK sizing each inch of difference moves the cup one letter, so 32D and 32DD share a band and differ by about an inch of bust. A cup letter means nothing without its band: a D on a 32 band holds less than a D on a 38 band.

This calculator follows the modern method of the r/ABraThatFits community (ABTF), as written in its Manual Sizing Guide. The band is your snug underbust, rounded to a whole inch and then to an even number: an odd reading of 37 or less goes up (33 becomes 34), and an odd reading of 39 or more goes down (39 becomes 38). The cup is the bust minus the loose underbust, one letter per inch, adjusted by half the gap between the loose underbust and the band, so rounding the band up by an inch takes half a cup off. Nothing is added to the band. With two measurements, the loose underbust is taken to equal the snug one.

The traditional US and UK method, as recorded in Wikipedia's Bra size article, adds 4 inches to an even underbust and 5 to an odd one before reading the cup. That gives a looser band and a smaller cup letter. A 2012 study in Ergonomics by White and Scurr compared it with professional best-fit sizing in 45 women and found that it overestimated band size and underestimated cup size, and more so as band size increased. The calculator prints the store answer for your own measurements in the line under the cards. With the default 32 in underbust and 37 in bust, the first card reads 32DD and that line reads “The old +4 method gives 36A. The same cups on band 36, 2 bands looser: 36C.” Set the size system to EU, FR/ES or IT and the same line follows the European standard EN 13402, which rounds the underbust to the nearest 5 cm and reads the cup in 2 cm steps.

Every result appears in six systems at once. US and UK bands share one number. EU bands go up in steps of 5 (UK 34 = EU 75), French and Spanish bands are the EU number plus 15 (FR/ES 90), Italian bands are small numbers (IT 3) and Australian and New Zealand bands sit 22 below the UK number (AU 12). Cup letters agree up to D and split above it: a US 36DDD is a UK 36E and an EU 80F. The sister-size table shows the same cup volume from two bands down to two bands up, and the collapsible band and cup charts highlight your row.

Two more paths share the page. “Use six measurements (more precise)” adds a loose and a tight underbust plus a leaning and a lying bust, the same six inputs as ABTF's own calculator. “Convert a size” takes a label you already wear and returns the same size in the other five systems with its sisters. Bands run from UK 28 to 56 and cups go up to UK MM, US P and EU U. Results update as you type; there is no button to press.

How to measure your bra size at home

Two tape readings decide the result, so take them with care. A soft tape measure and a mirror are enough.

1. Measure with no bra, or in a non-padded one. Padding adds to the bust reading and pushes the cup letter up.

2. Keep the tape level all the way around. A tape that sits lower at the back than at the front reads long, and a long underbust gives a looser band.

3. Snug underbust: wrap the tape under the bust and pull it as snug as you would want a bra band to feel, breathing normally. The band comes from this reading.

4. Bust: stand upright and run the tape loosely around the fullest point, without pressing in.

5. Take each measurement twice. If the two readings differ, type the average.

The snug underbust sets the band, and two of the five lines under “Check the fit” are about the band: “The band rides up at the back: go one band down and one cup up.” and “The straps carry most of the weight: go one band down.” A band read too loose at this step shows up later as those two problems.

Switching on “Use six measurements (more precise)” adds four fields and swaps the five steps for a six-step list, “How to take the six measurements”. The loose underbust goes in the same place as the snug one, with the tape resting level and not pulling. The tight underbust is pulled as tight as it goes after breathing out, and it is the only reading taken that way. The leaning bust is measured bent forward from the waist until your back is level, and the lying bust on your back. The new fields open pre-filled from your two readings, so overwrite each one with its own measurement.

One person's measurements, from tape to the sizes to try

Take someone with a 34 in snug underbust and a 38 in bust whose drawer holds 38B bras. The page opens in inches with the size system on US, so they type 34 into “Underbust, snug” and 38 into “Bust, standing”. The results change as each digit goes in; there is no button.

The first card, “Your starting size (US)”, reads 34D, with the method line “Modern fitting (snug underbust, no +4), as used by r/ABraThatFits” under the size. The second card, “One band up, often more comfortable”, reads 36C.

The 38B from the drawer appears in the line under the cards: “The old +4 method gives 38AA. The same cups on band 38, 2 bands looser: 38B.” Those bras carry the cup volume of a 34D on a band two sizes looser. If they ride up at the back, that gap is the reason.

The tiles under “The same size in other systems” turn 34D into EU (Germany, Poland) 75D, FR/ES (France, Spain) 90D, IT (Italy) 3D, UK (Britain, Ireland) 34D and AU (Australia, NZ) 12D. The “Sister sizes” table lists 30DDD, 32DD, 34D (highlighted), 36C and 38B.

One bra in the drawer comes from a French brand and is labeled 90B. In “Convert a size”, with “Size system on your label” set to FR/ES (France, Spain), band 90 and cup B, the tiles read US 34B: the right band, with cups two letters smaller than the starting size.

The callout under the table says to try the starting size and its sister sizes, then check the fit. For this person that means 34D first, 36C if a 34 band feels too firm, and 32DD if the 34 band still rides up.

The math behind the band and the cup

\text{band} = \operatorname{even}\big(\operatorname{round}(U_s)\big) \qquad i = P - U_l + \tfrac{1}{2}\operatorname{round}(U_l - \text{band})

$U_s$ = Snug underbust in inches. Centimeters are divided by 2.54 first, because the method is defined in inches.
$\operatorname{even}$ = Turns an odd whole number into an even band: up by 1 for 37 and below, down by 1 for 39 and above.
$U_l$ = Loose underbust in inches. With two measurements it equals the snug underbust; in six-measurement mode it is its own reading and cannot be smaller than the snug one.
$P$ = Bust in inches. With two measurements, the standing bust. With six, the leaning bust, or the average of the standing, leaning and lying readings when the leaning one is more than 2.5 in above the standing one.
$i$ = Cup index, rounded half up for the size on the card: 0 = AA, 1 = A, 2 = B, 3 = C, 4 = D, 5 = DD, 6 = DDD in US sizes, which is E in UK sizes and F in EU sizes.

In words, the band is the snug underbust rounded to an even inch, and the cup counts the inches between the bust and the loose underbust, corrected by half the gap between the loose underbust and the band.

The default state is a 32 in underbust and a 37 in bust. 32 is already even, so the band is 32 and the correction is zero:

i = 37 - 32 + \tfrac{1}{2}(0) = 5

Index 5 is DD in US and UK sizes and E in EU sizes, so the first card reads 32DD and the EU tile reads 70E.

If the index lands between two letters, the card rounds half up and a note names both. With 30 in and 35.5 in the index is 5.5: the card reads 30DDD and the note says “Between 30DD and 30DDD: try both.” The note appears once the index sits between a quarter and three quarters of the way from one letter to the next.

The store line uses the old arithmetic. Under +4, the 32 in underbust becomes a 36 band and the cup is 37 − 36 = 1 inch, an A, hence “The old +4 method gives 36A.” Its second half moves the modern cups onto that band with the sister rule, two bands up and two cups down, so 32DD becomes 36C.

Worked examples from real measurements

Five measurements: the modern size against the +4 store size

All five use two measurements in inches with the size system on US. The last two columns are the line printed under the cards.

Underbust / bust	Starting size (US)	Old +4 method	Same cups on the +4 band
30 / 36 in	30DDD	34B	34D
32 / 37 in	32DD	36A	36C
34 / 38 in	34D	38AA	38B
36 / 42 in	36DDD	40B	40D
38 / 44 in	38DDD	42B	42D

In every row the +4 band is 4 inches larger and its cup letter four steps smaller, because the extra inches come straight off the bust-minus-band difference. The last column moves the same cup volume onto the looser band. A person who wears the size in that column and finds the band riding up has the size in the second column as the next one to try.

Measuring in centimeters: 80 cm underbust, 92 cm bust

With the unit on cm and the size system left on US, 80 and 92 give 32D on the first card and 34C on “One band up, often more comfortable”. The tiles read EU (Germany, Poland) 70D, FR/ES (France, Spain) 85D, IT (Italy) 2D, UK (Britain, Ireland) 32D and AU (Australia, NZ) 10D, and the store line reads “The old +4 method gives 36AA. The same cups on band 36, 2 bands looser: 36B.”

Type the same 80 and 92 with the unit still on in and no size appears. Both fields show “Looks like centimeters: switch the unit to cm” and the card note reads “A measurement looks like it’s in the other unit.” Set the unit before typing and the problem never comes up.

Where US and UK letters split: 36 in underbust, 42 in bust

The first card reads 36DDD (US). The tiles give UK (Britain, Ireland) 36E, EU (Germany, Poland) 80F, FR/ES (France, Spain) 95F, IT (Italy) 4F and AU (Australia, NZ) 14E, three different letters for one cup. The highlighted row of “Cup sizes by system” reads F, E, DDD and E across its EU/FR/ES/IT, UK, US and AU columns. The sister sizes run 32H, 34G, 36DDD, 38DD and 40D, and the old +4 method would give 40B.

The chart caption gives the practical rule: up to D all systems agree, and above it brands grade cups differently, so the brand's own chart has the last word.

A cup past the end of the US scale: 30 in underbust, 47 in bust

The US letters in this calculator stop at P, and this cup lands beyond it. The first card shows UK 30L with two notes: “US sizes stop at P. This is the UK size, which brands making these cups use.” and “Large cups and averaged measurements are less precise: treat this as a starting point.”

The second card shows 32P. The tiles give EU (Germany, Poland) 65R, FR/ES (France, Spain) 80R, IT (Italy) 1R and UK (Britain, Ireland) 30L, while the AU tile shows a dash because the Australian letters here end at H. The sister table keeps only the rows that have a US label, 32P and 34O, and the store line reads “The old +4 method gives 34M.” For cups this size, shop by the UK label the card gives.

Six measurements: loose 78, snug 76, tight 73, standing 92, leaning 94, lying 91 cm

With “Use six measurements (more precise)” on and the unit on cm, the first card reads 30G (US) and the second 32DDD. The tiles give EU (Germany, Poland) 65G, FR/ES (France, Spain) 80G, IT (Italy) 1G, UK (Britain, Ireland) 30F and AU (Australia, NZ) 8F.

The snug 76 cm rounds to a 30 band. The cup is read from the leaning bust, 94 cm, because it is less than 2.5 in above the standing 92 cm, so no averaging happens. The tight reading is 3 cm under the snug one, close enough to add the note “Your snug and tight underbust are close: if bands feel tight, try one band up.” The second card, 32DDD, is that band-up option with the same cups.

Converting a label you already own: UK 34DD

In “Convert a size”, set “Size system on your label” to UK (Britain, Ireland), “Band” to 34 and “Cup” to DD. This mode shows no cards. The tiles give EU (Germany, Poland) 75E, FR/ES (France, Spain) 90E, IT (Italy) 3E, US 34DD and AU (Australia, NZ) 12DD, and the sister table lists 30F, 32E, 34DD, 36D and 38C in UK sizes.

Going the other way, an EU 75E label converts to UK 34DD and US 34DD. A UK DD is an EU E because the European scale doubles no letter after AA: it goes D, E, F, G, where the UK goes D, DD, E, F, FF.

Bra size chart: common sizes in US, UK, EU, FR/ES, IT and AU

US	UK	EU	FR/ES	IT	AU
30DDD	30E	65F	80F	1F	8E
30G	30F	65G	80G	1G	8F
32D	32D	70D	85D	2D	10D
32DD	32DD	70E	85E	2E	10DD
34B	34B	75B	90B	3B	12B
34C	34C	75C	90C	3C	12C
34D	34D	75D	90D	3D	12D
34DD	34DD	75E	90E	3E	12DD
36DDD	36E	80F	95F	4F	14E
38DDD	38E	85F	100F	5F	16E

Measuring and sizing mistakes that skew the result

Adding 4 inches before you type. Enter the tape reading itself. A 32 in underbust typed as 36, with a 37 in bust, moves the band two sizes looser and the cup four steps smaller, which is the 36A the store line already shows for those measurements.
Measuring over a padded bra. Padding adds to the bust reading and pushes the cup letter up. Measure with no bra or a non-padded one.
A tape that drops at the back. A tape lower behind you than in front reads long on the underbust, and the band comes out looser. Check the back in a mirror.
Pulling the two-measurement underbust as tight as it goes. The snug reading should feel like a band you would wear, taken while breathing normally. The as-tight-as-possible reading belongs only in the “Underbust, tight (breathe out)” field of six-measurement mode.
Typing centimeters with the unit on in. The calculator flags it under the field with “Looks like centimeters: switch the unit to cm” and shows no size until the unit matches the numbers.
Reading the cup letter as a fixed volume. A D on a 34 band and a D on a 38 band are different cups. Compare sizes through the sister-size table instead: with the default measurements, 32DD, 34D and 36C hold the same cups.
Treating an F as the same cup on every label. A UK F is one cup larger than an EU F: UK 30F is EU 65G, and EU 80F is UK 36E. Read which system the label uses before you compare letters.

What a tape measure cannot tell you

Two circumferences describe the size of a ribcage and a bust. They say nothing about breast shape, how far the tissue projects from the chest, how wide the root is at the sides, or how a given brand grades its cups, and those decide whether one particular bra fits. The callout under the sister-size table puts it in one line: “A starting size, not a guarantee: brands and styles cut differently.”

Measured sizes carry a documented error. McGhee and Steele (2010) checked 104 women against professional fitting criteria and found 85% in ill-fitting bras, and both the sizes the women chose themselves and the sizes from bra-sizing measurement systems differed from the correct size. This calculator is also a tape-measure method, though not one the study tested, so it hands you a set of sizes to try: the starting size, the band-up card and the sister sizes around them.

Precision drops at the edges. From UK GG upward, and whenever the bust readings were averaged, the card adds “Large cups and averaged measurements are less precise: treat this as a starting point.” A band outside UK 28 to 56 gets no size and the note “Outside standard band sizes (28 to 56).”, a cup below AA gets “Smaller than AA: choose by band size (a bralette, for example).” and a cup past UK MM gets “Beyond standard charts: a specialist bra fitter can help.”

The calculator covers the EU, FR/ES, IT, UK, US and AU systems. It has no Japanese, Korean or Chinese sizes and no brand-specific charts, and it does not size sports, nursing or swim bras separately. Measure again whenever your bras start to fit differently, because the result is only as current as the tape readings behind it.

Bra size questions

How do I measure my bra size at home?

Use a soft tape, with no bra or a non-padded one. Measure the underbust under the bust, as snug as you'd want a band to feel and breathing normally, then the bust loosely around the fullest point while standing. Measure twice and type the averages.

Do I add 4 inches to my underbust?

No. Type the snug underbust as the tape reads it. Adding 4 or 5 inches is the old store-chart method, and this calculator already prints what that method would give in the line under the cards, so you can compare the two without doing the arithmetic.

What bra size am I with a 32 inch underbust and a 37 inch bust?

32DD in US sizes, which is also UK 32DD, EU 70E, FR/ES 85E, IT 2E and AU 10DD. Its sister sizes include 30DDD and 34D, and 34D is the second card, “One band up, often more comfortable”. The old +4 method would call the same measurements 36A.

What are sister sizes, and is 34D the same as 32DD?

Sister sizes hold the same cup volume on a different band: one band down and one cup up, or one band up and one cup down. 34D and 32DD are sisters, so the cups match while the 32DD band is 2 inches tighter. 36C is the sister on the other side, and 30DDD and 38B sit two steps away. They are different sizes with the same cups. Reach for a sister when the cups fit and the band does not: a band that rides up points to the smaller band, a band that feels too firm to the larger one.

Is a US DDD the same as a UK E or an F?

In this calculator a US DDD is a UK E and an F in EU, French, Spanish and Italian sizes: US 36DDD shows as UK 36E and EU 80F. A UK F is one cup larger, a US G. Above D, US brands also differ among themselves: Wikipedia's Bra size article records US makers using the DDD, G, H sequence this calculator follows, a DDDD sequence, numbered cups from D1 up, or the British sequence. Check which system a label uses before comparing letters.

How do I convert a bra size, for example EU 70D to US?

Switch to “Convert a size”, choose the system printed on the label, then the band and the cup. EU 70D is US 32D, which is also UK 32D, FR/ES 85D, IT 2D and AU 10D. The tiles show the other five systems, and the table under them lists the sister sizes in the label's own system. For rings and shoes, the ring size converter and the shoe size converter convert sizes between countries.

Should I round an odd underbust measurement up or down?

The calculator does it for you, the way ABTF's calculator does. It rounds the snug underbust to a whole inch, then moves an odd number to an even band: up for 37 and below (33 becomes 34) and down from 39 (39 becomes 38, 41 becomes 40). Rounding the band up takes half a step off the cup and rounding it down adds half a step, so the cup volume stays where your measurements put it.

Why does this calculator give a smaller band and a bigger cup than store charts?

Store charts start from a looser band. The traditional US and UK method adds 4 or 5 inches to the underbust, and continental charts that follow EN 13402 round the underbust to the nearest 5 cm and use it as the EU band (80 cm gives EU 80, which the band chart lists as UK 36); both land one to three bands looser than modern fitting, most often two, and a cup read against a looser band comes out with a smaller letter. White and Scurr (2012) found the traditional method overestimated band size and underestimated cup size in 45 women, more so at larger bands. The line under the cards gives the store size for the measurements you typed.

What should I do if the calculator says I'm between two cup sizes?

Try both. A note such as “Between 30DD and 30DDD: try both.” appears when your cup falls near the middle between two letters; with a 30 in underbust and a 35.5 in bust, the card shows 30DDD and the note names 30DD as well. The fit check under the results settles it: cups that gape or wrinkle mean the smaller cup, and a center panel that lifts away from the chest means the larger one.

Why does my bra band ride up at the back?

In the fit check on this page, a band riding up is the sign of a band that is too loose: “The band rides up at the back: go one band down and one cup up.” From 34D that means 32DD, the sister size with the same cups on a tighter band. Straps that carry most of the weight call for the same band change.

When is the six-measurement mode worth using?

It changes the result most when your leaning bust differs from your standing one, because in that mode the cup is read from the leaning bust. If the leaning reading is more than 2.5 in above the standing one, the three bust readings are averaged and a note says so. The gap between snug and tight underbust drives two band notes as well: under 2 in suggests one band up if bands feel tight, and 4 in or more says one band down may suit you.

Is it true that 80% of women wear the wrong bra size?

Wikipedia's Bra size article gives 80 to 85%, citing a 2008 paper it tags as a possibly unreliable source. A peer-reviewed figure in the same range comes from McGhee and Steele (2010): 85% of 104 women were wearing ill-fitting bras when checked against professional fitting criteria. That is one sample of 104 people, so treat the round 80% as a rough estimate and judge your own fit with the fit check on this page.

How accurate is this bra size calculator?

It reproduces the r/ABraThatFits method, and in testing its sizes matched ABTF's live calculator on 35 underbust values from 62 to 130 cm. The method is still a tape-measure estimate: McGhee and Steele (2010) found that sizes from the bra-sizing measurement systems in their study differed from the size set by professional fitting criteria. Treat the result as the first size to try, then use the sister sizes and the fit check to refine it.

Is this bra size calculator free, and does it save my measurements?

It is free and needs no account, and there is no profile to save to. The values you change are written into the page address, so a copied link reopens the same result on another device, while the default measurements leave the address clean.

Sources & References

Content verified by the Smart Calculators Team

EU	FR/ES	IT	UK/US	AU
60	75	0	28	6
65	80	1	30	8
70	85	2	32	10
75	90	3	34	12
80	95	4	36	14
85	100	5	38	16
90	105	6	40	18
95	110	7	42	20
100	115	8	44	22
105	120	9	46	24
110	125	10	48	26
115	130	11	50	28
120	135	12	52	30
125	140	13	54	32
130	145	14	56	34

EU	FR/ES	IT	UK/US	AU
60	75	0	28	6
65	80	1	30	8
70	85	2	32	10
75	90	3	34	12
80	95	4	36	14
85	100	5	38	16
90	105	6	40	18
95	110	7	42	20
100	115	8	44	22
105	120	9	46	24
110	125	10	48	26
115	130	11	50	28
120	135	12	52	30
125	140	13	54	32
130	145	14	56	34

EU	FR/ES	IT	UK/US	AU
60	75	0	28	6
65	80	1	30	8
70	85	2	32	10
75	90	3	34	12
80	95	4	36	14
85	100	5	38	16
90	105	6	40	18
95	110	7	42	20
100	115	8	44	22
105	120	9	46	24
110	125	10	48	26
115	130	11	50	28
120	135	12	52	30
125	140	13	54	32
130	145	14	56	34