42 Bra Size: Every Cup on a 42 Band
42 is squarely plus-range territory, where the choice narrows to brands that engineer specifically for it. A 42 scaled up from a 34 pattern by a grading rule rather than redrawn tends to fail in predictable ways, and a lot of mainstream 42s are exactly that.
Are you really a 42?
Measure snug and level directly under the bust, with no bra on or a non-padded one, and breathe normally. A reading between 41 and 43 inches (104-109 cm) is a 42 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 46.
A 41 or 43 inch reading is worth taking sitting as well as standing, because the ribcage measurement moves more here than at smaller bands. Fit the standing measurement; a band that only works seated will ride up the moment you stand.
If the tape and the tag disagree, the calculator settles it in two measurements, and how to measure covers the technique in detail.
Every 42 size, in every system
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 42 band
Judge a 42 by its frame before its cup: side wing height, hook count, and whether the band is cut with any shaping at all. Brands that redraw rather than scale advertise it, because it is expensive and it is the only reason to pay their price.
The fit problem this band produces most
Asymmetry becomes more noticeable at this band simply because there is more volume for a difference to express itself in. Fit the larger side and adjust the smaller with the strap; sizing to the smaller side compresses the larger one all day.
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 42D 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 42 band, D works out at roughly 912 cc per cup, against 608 cc for 28D - a difference of about 50% from the same letter. Across every band this site charts:
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 42
If a 42 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.
Frequently asked questions
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.