38 Bra Size: Every Cup on a 38 Band

Fits an underbust of

37-39 in

94-99 cm

Called this elsewhere

EU 85

FR 100 · AU 16 · JP 85

Cup pages on this band

38B through 38DDD

38 is a genuine boundary in how bras are built. Below it, most ranges rely on the wire and a two-hook band; at 38 and above, construction starts carrying the load, and the gap between a well-engineered band and a cheap one becomes something you feel by mid-afternoon rather than something you notice in a mirror.

Are you really a 38?

Measure snug and level directly under the bust, with no bra on or a non-padded one, and breathe normally. A reading between 37 and 39 inches (94-99 cm) is a 38 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 42.

At 37 or 39 inches the tape is easy to pull too tight over a fuller ribcage, which reads a band smaller than you wear. Snug means it does not slide, not that it compresses. If the two readings differ by more than an inch, take the looser one.

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

Every 38 size, in every system

Size	UK	EU	FR	AU	JP	KR	Volume
38B	38B	85B	100B	16B	C85	C85	206 cc
38C	38C	85C	100C	16C	D85	D85	464 cc
38D	38D	85D	100D	16D	E85	E85	825 cc
38DD	38DD	85E	100E	16DD	F85	F85	1289 cc
38DDD	38E	85F	100F	16E	G85	G85	1857 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 38 band

Three hooks should be the baseline at this band, and taller side wings matter more than any fabric or fashion detail. A 38 with a two-hook band and narrow wings will roll no matter how correct the tag is.

The fit problem this band produces most

Band rolling and the double-boob effect both cluster at 38, and they have opposite causes: rolling means the band is under-built for the load, while the double-boob means the cup edge is cutting across tissue it should be containing.

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 38D is not the same size as 28D

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 38 band, D works out at roughly 825 cc per cup, against 608 cc for 28D - a difference of about 36% 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 38

If a 38 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 (36)	Looser band (40)
38B	36C	not charted
38C	36D	not charted
38D	36DD	40C
38DD	36DDD	40D
38DDD	36F	40DD

Frequently asked questions

What underbust measurement is a 38 band?

Roughly 37 to 39 inches (94-99 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 38 band the same in UK and European sizing?

The UK uses the same 38, but Europe calls it 85, France 100, Australia 16, and Japan and Korea 85. Only the cup letters change further, and they change differently in each system.

Does a 38D mean the same size as a 36D?

No. A cup letter is a difference, not a volume, so it scales with the band it sits on. 38D holds about 825 cc per cup, while 28D holds about 608 cc - roughly 36% 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 42. Why does this page say 38?

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 37-39 inch underbust ends up in a 42. If you were fitted that way, your real starting size is likely a 38 with a fuller cup letter than you are used to.

Other bands

28 band 30 band 32 band 34 band 36 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.