42C Bra Size
42C fits a 41–43 inch (104–109 cm) underbust and a full bust of about 46 inches (117 cm). Its sister sizes are 40D and 44B.
Last reviewed on 25 September 2026.
42C at a glance
| Underbust (band) | 41–43 in · 104–109 cm |
|---|---|
| Full bust | ≈ 46 in · 117 cm |
| Bust minus underbust | ≈ 4 in · 10 cm |
| Sister sizes (same cup volume) | 40D · 44B |
| UK / EU / FR / AU | 42C · 95C · 110C · 20C |
| One cup bigger | 42D |
| One cup smaller | 42B |
| Approx. top size | XXL / 1X · UK 18–20 / US 14–16 |
Measurements for 42C
42C is built for an underbust ribcage measurement that falls in the 41–43 inch range, with a full-bust measurement around 46 inches. The band number — 42 — is a larger band where reinforced construction starts to matter for long-day comfort. The cup letter — C — describes the difference between the two measurements; a C cup means the full bust is about four inches larger than the underbust — this is the threshold where cup shape (full-cup, demi, balconette, plunge) starts to make a noticeable difference.
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42C in Other Sizing Systems
EU, FR, and JP sizing read the band in centimetres, which is why 42C maps to 95C (EU), 110C (FR), and 95C (JP) — the same body, expressed in different units. AU sizing uses a small numeric scale (20C for this band). UK sizing shares the band number with the US but parts ways at the cup once you go past D, so 42C reads as 42C on a UK label.
Sister Sizes for 42C
These sizes have the same cup volume as 42C. Try them if the band feels too tight or too loose.
← Tighter band, bigger cup · Looser band, smaller cup →
Sister sizes are useful when the cup of your 42C fits well but the band is wrong — too loose by the end of the day, or too tight to clip up comfortably. Going one band smaller and one cup larger keeps the cup volume the same while tightening the band; going the other way loosens the band without losing cup space. Read the full sister-size matrix if you want to see how this works for every size at once.
Fit Tips for 42C
C cups work well across most bra styles. If you spill over in one brand but fit fine in another, cup shape and depth vary by maker — the size on the label is only part of the story.
If your 42C bra is gapping at the top of the cup, the cup may be too large or the wrong shape — try a demi-cup or balconette before assuming the size is wrong. If the centre piece between the cups (the gore) does not lay flat against your sternum, the cup is almost certainly too small; go up one cup. If the band rides up across your back during the day, the band has stretched out or was too loose to begin with — drop one band size and add one cup to keep the same cup volume.
For more detailed troubleshooting, the Fit Test on the home page covers six common visible problems and the size or shape change that usually addresses each one. The guide to measuring mistakes covers the most common reasons a calculation comes out wrong in the first place.
Related sizes
If 42C is close but not quite right, these neighbouring sizes are the most useful next places to look:
See every size at a glance on the full bra size index, or read how to measure your bra size if you are not sure 42C is right for you.
42C — frequently asked questions
What measurements are a 42C bra in inches and cm?
A 42C bra fits an underbust (ribcage) measurement of roughly 41 to 43 inches (104–109 cm) and a full-bust measurement of about 46 inches (117 cm). The cup letter C reflects the roughly 4-inch (10 cm) difference between those two numbers.
What size is equivalent to 42C? (sister sizes)
The sister sizes of 42C are 40D (tighter band, one cup letter up) and 44B (looser band, one cup letter down). They hold the same cup volume as 42C on a different band. Try a sister size when the cups of your 42C fit but the band feels too loose or too tight.
What is 42C in UK, EU, and other sizing systems?
42C (US) converts to 42C in UK sizing, 95C in EU sizing, 110C in French sizing, 20C in Australian sizing, and 95C in Japanese sizing. The body is the same; only the labelling system changes.
Is 42C a small or large bra size?
In terms of how common it is, this size pairs an above-average band with a mid-range cup. There is no universal "small" or "large" bra size — the same cup letter describes a different volume on every band — but within the full range BraCalc covers (bands 28–48, cups AA–H) this combination sits toward the middle end.
Is 42C a small, medium, large, or XL?
As a rough guide, a 42 band usually matches size XXL / 1X in tops and bralettes — around UK dress size 18–20 (US 14–16). The band number drives this more than the cup letter, so 42C lands in the same letter size as other 42-band bras. Letter sizing varies a lot between brands, so always check the brand's own chart.
What is the next size up or down from 42C?
Keeping the same 42 band, one size up in the cup is 42D, and one size down is 42B. If you want a bigger or smaller band but the same cup volume, use a sister size instead: 40D or 44B. Remember that the cup letter is relative to the band — 44C has more cup volume than 42C, not the same.
Not sure about your size? Measure yourself and double-check.
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