36B vs 38A
Same cup volume, different band: sister sizes. Here is exactly what changes, and when to move between them.
36B or 38A, in short
36B and 38A are sister sizes: the same cup volume on a band two inches longer. Move to 38A if the 36 band digs in; move to 36B if the 38 band rides up. The cups themselves don't change.
36B and 38A, side by side
Same dome, different band bar: the cups hold the same volume; the band is two inches longer.
From 36B to 38A, or back
- The 36 band digs in or leaves marks by evening
- You are on the loosest hook and it still feels tight
- The cups fit perfectly, no gape, no spill
- The 38 band rides up at the back
- You fasten it on the tightest hook from new
- Straps are carrying the weight
Sister sizes share volume, not shape. The wire on 36 is narrower and more projected; on 38 wider and shallower. Narrow roots usually prefer the snugger sister; wide roots the looser one.
Brands that carry both 36B and 38A
Range-checked against each brand's core collections, with both sizes written in the brand's own notation.
| Brand | 36B as | 38A as | System | How it runs |
|---|---|---|---|---|
| Wacoal | 36B | 38A | US | Band true to size · cups true |
| Natori | 36B | 38A | US | Band soft / stretchy · cups grades small |
| Le Mystère | 36B | 38A | US | Band firm · cups true |
| Victoria's Secret | 36B | 38A | US | Band soft / stretchy · cups grades small |
| Maidenform | 36B | 38A | US | Band true to size · cups true |
| Soma | 36B | 38A | US | Band true to size · cups true |
| ThirdLove | 36B | 38A | US | Band true to size · cups grades generous |
| Savage X Fenty | 36B | 38A | US | Band soft / stretchy · cups true |
| Aerie | 36B | 38A | US | Band true to size · cups true |
| Cuup | 36B | 38A | US | Band true to size · cups true |
Every brand page converts your measured size and notes how it runs. All bra brands →
36B and 38A in every system
| US | UK | EU / DE / JP | FR / ES | AU / NZ | IT |
|---|---|---|---|---|---|
| 36B | 36B | 80B | 95B | 14B | 4B |
| 38A | 38A | 85A | 100A | 16A | 5A |
Sister sizes stay sisters in every system: the band moves one step and the cup one letter, whatever the alphabet.
The five fit checks, 36B vs 38A
| Check | What right looks like | What it tells you here |
|---|---|---|
| Band | Level, snug on the loosest hook, two fingers underneath, no ride-up | Both bands should pass this; the one that rides up or digs is the wrong sister |
| Cups | Filled to the top edge with no gap and no spill | Should look identical in both: the volume is the same |
| Gore | Flat against the sternum | Same in both |
| Straps | Light duty, no digging | Digging in the 38 band means the band is loose: take the snugger sister |
| Wire | On the ribcage, not on tissue | Narrower on 36, wider on 38: pick by breast root |
What goes wrong choosing between 36B and 38A
| Mistake | Why it fails |
|---|---|
| Going to 38A because the cups spill | Sister sizes hold the same volume: spillage needs a cup up on the same band, not the looser sister |
| Choosing the looser sister for comfort | A band that is comfortable on day one is loose by month three; the snugger sister on the loosest hook is the durable choice |
| Ignoring wire width | Same volume, different wire: narrow roots dig in the wider sister, wide roots pinch in the narrower one |
Availability, shape and the +4 check
Related comparisons
36B vs 38A: answered
What is the difference between 36B and 38A?
They are sister sizes: the same cup volume on a band two inches longer. 36B is a 36″ band with a 2″ difference; 38A is a 38″ band with a 1″ difference.
Is 36B bigger than 38A?
Same volume; 38A has the longer band and will feel looser.
Can I wear 38A instead of 36B?
Yes: that is what sister sizes are for. Move when the cups fit but the band is wrong.
What are 36B and 38A in UK and EU sizing?
36B: UK 36B, EU 80B, FR 95B. 38A: UK 38A, EU 85A, FR 100A.
Do 36B and 38A fit the same in every brand?
The relationship holds everywhere; the fit doesn't. Brands with soft bands push you toward the snugger sister, firm bands toward the looser; brands whose cups grade small push you up a cup. The brand table above shows how each runs.
Which is more common, 36B or 38A?
36B is one of the most widely stocked sizes; 38A is less common in mainstream stores.
Should I own both 36B and 38A?
Some people do: the snugger sister for structured, wired styles and the looser for soft or wireless ones. Same volume, so both fit the cups.
How do I measure to tell 36B from 38A?
Underbust snug (34.5–36.4″ gives band 36; 36.5–38.4″ gives 38), bust at the fullest point; the difference sets the cup. Then confirm on the body with the five fit checks.
HauteFlair labels cups in UK letters, so these links already convert your size by position (a US DDD lands on a UK E, a US G on a UK F). HauteFlair is owned by the same company as Brasize.ai; that relationship never changes the sizing math, charts, or fit advice on this page. How this site makes money.
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