40H Bra Size
Everything you need to know about bra size 40H — measurements, sister sizes, international equivalents, and fit advice.
Last reviewed on 28 April 2026.
Measurements for 40H
40H is built for an underbust ribcage measurement that falls in the 39–41 inch range, with a full-bust measurement around 49 inches. The band number — 40 — is a larger band where reinforced construction starts to matter for long-day comfort. The cup letter — H — describes the difference between the two measurements; an H cup means the full bust is about eight inches larger than the underbust — well-engineered bands and reinforced wires are typically what hold a bra steady for a full day at this size.
40H in Other Sizing Systems
EU, FR, and JP sizing read the band in centimetres, which is why 40H maps to 90H (EU), 105H (FR), and 90H (JP) — the same body, expressed in different units. AU sizing uses a small numeric scale (18FF for this band). UK sizing shares the band number with the US but parts ways at the cup once you go past D, so 40H reads as 40FF on a UK label.
Sister Sizes for 40H
These sizes have the same cup volume as 40H. 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 40H 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 40H
H cups call for maximum-support construction: reinforced bands, wider straps, and side panels. Specialist fuller-bust ranges are usually the most reliable source of styles in this cup.
If your 40H 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 40H 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 40H is right for you.
40H — frequently asked questions
What measurements are a 40H bra?
A 40H bra fits an underbust (ribcage) measurement of roughly 39 to 41 inches (99–104 cm) and a full-bust measurement of about 49 inches (124 cm). The cup letter H reflects the difference between those two numbers.
What are the sister sizes of 40H?
The sister sizes of 40H are 38H and 42F. They share the same cup volume as 40H but use a different band — go to 38H for a tighter band, or up for a looser one. Try a sister size when the cup of your 40H fits but the band feels too loose or too tight.
What is 40H in UK, EU, and other sizing systems?
40H (US) converts to 40FF in UK sizing, 90H in EU sizing, 105H in French sizing, 18FF in Australian sizing, and 90H in Japanese sizing. The body is the same; only the labelling system changes.
Is 40H a small or large bra size?
In terms of how common it is, this size pairs an above-average band with a fuller-bust 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 fuller end.
Not sure about your size? Measure yourself and double-check.
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