34 Bra Size: Every Cup on a 34 Band

Fits an underbust of

33-35 in

84-89 cm

Called this elsewhere

EU 75

FR 90 · AU 12 · JP 75

Cup pages on this band

34A through 34K

34 is the band brands design their base pattern around and grade outward from, which is why a 34 in almost any range fits more predictably than the same style two bands away in either direction. It is also the number most often quoted in average-size surveys, though those averages move with method and country.

Are you really a 34?

Measure snug and level directly under the bust, with no bra on or a non-padded one, and breathe normally. A reading between 33 and 35 inches (84-89 cm) is a 34 band. Nothing is added to that number: the "+4" rule was written for rigid 1950s fabric and on modern elastic it produces a band about two sizes too loose, which is how the same measurement used to be sold as a 38.

33 and 35 inch readings are the most common between-band results on this site, and 34 is where brands are most consistent, so trying the 34 first gives the cleanest answer. If a 34 rides up on the loosest hook, the band is not the problem: check whether the cup is too small and pulling the back upward.

If the tape and the tag disagree, the calculator settles it in two measurements, and how to measure covers the technique in detail.

Every 34 size, in every system

Size	UK	EU	FR	AU	JP	KR	Volume
34A	34A	75A	90A	12A	B75	B75	46 cc
34B	34B	75B	90B	12B	C75	C75	185 cc
34C	34C	75C	90C	12C	D75	D75	415 cc
34D	34D	75D	90D	12D	E75	E75	738 cc
34DD	34DD	75E	90E	12DD	F75	F75	1154 cc
34DDD	34E	75F	90F	12E	G75	G75	1661 cc
34F	34F	75G	90G	12F	H75	H75	2261 cc
34I	34G	75I	90I	12G	J75	J75	3738 cc
34K	34H	75K	90K	12H	L75	L75	5584 cc

Every size in the first column has its own page with sister sizes, a volume comparison and shopping notes. Volumes are estimates from the model on the weight page.

Buying at a 34 band

Because it is the grading anchor, a 34 is the most reliable band to try a new brand in. If a house fits you badly at 34, it will usually fit you worse elsewhere on its ladder rather than better.

The fit problem this band produces most

The most common problem at 34 is not the band at all - it is inheriting the letter from an old bra and never rechecking it. Cup requirements drift over years while the band number stays memorable.

Work through it with the fit problem solver, or read the full list of fit problems if you are not sure which one you have.

Why 34D is not the same size as 42D

A cup letter records the difference between bust and underbust, not a volume, so the same letter grows with the band underneath it. On a 34 band, D works out at roughly 738 cc per cup, against 912 cc for 42D - a difference of about 24% from the same letter. Across every band this site charts:

28D · 608 cc30D · 651 cc32D · 695 cc34D · 738 cc36D · 782 cc38D · 825 cc40D · 869 cc42D · 912 cc

This is also why sister sizing works: dropping a band and adding a letter keeps the volume roughly constant. See sister sizes explained for the full ladder.

Sister sizes for every 34

If a 34 band rides up, the sister on the tighter band is the one to try; if it digs, go the other way. Both hold roughly the cup volume you already wear.

Your size	Tighter band (32)	Looser band (36)
34A	32B	not charted
34B	32C	36A
34C	32D	36B
34D	32DD	36C
34DD	32DDD	36D
34DDD	32F	36DD
34F	not charted	36DDD
34I	not charted	not charted
34K	not charted	not charted

Frequently asked questions

What underbust measurement is a 34 band?

Roughly 33 to 35 inches (84-89 cm) measured snug and level directly under the bust, with no bra or a non-padded one. Modern sizing adds nothing to that number: your band is your measurement, rounded to the nearest even size.

Is a 34 band the same in UK and European sizing?

The UK uses the same 34, but Europe calls it 75, France 90, Australia 12, and Japan and Korea 75. Only the cup letters change further, and they change differently in each system.

Does a 34D mean the same size as a 32D?

No. A cup letter is a difference, not a volume, so it scales with the band it sits on. 34D holds about 738 cc per cup, while 42D holds about 912 cc - roughly 24% different for the same letter. That is why moving a band without moving the letter changes the fit twice over.

I was measured as a 38. Why does this page say 34?

The old fitting method added four inches to the underbust measurement, which was designed for the rigid fabrics of the 1950s. On elastic modern bands it produces a band roughly two sizes too loose, which is how a 33-35 inch underbust ends up in a 38. If you were fitted that way, your real starting size is likely a 34 with a fuller cup letter than you are used to.

Other bands

28 band 30 band 32 band 36 band 38 band 40 band 42 band

Highlighted bands are this one's sister bands: the same cup volume sits on them one letter up or down. Not sure which band you are? Use the calculator.

Last updated August 2026.