A 38B is a wide band with a low cup letter, and almost everything people get wrong about it comes from reading the letter first. On a band this wide, a B is not a small cup.
Our bra size calculator works out the band and the letter together, along with the sizes either side.
What a 38B measures
Indian band sizing is your underbust rounded up to an even number plus four inches. A 38 band is cut for an underbust of about 33 to 34 inches.
The letter is the difference between bust and band. B is one to two inches.
| Inches | Centimetres | |
|---|---|---|
| Underbust | 33 to 34 | 84 to 86 |
| Bust | 39 to 40 | 99 to 102 |
| Difference | 1 to 2 | 3 to 5 |
On UK and US charts, which use the underbust itself as the band, the same body is a 34DD; EU charts call it a 75E. The bra size converter lines up all four systems.
A B cup on a 38 is not a small cup
This is the part that matters. A cup letter is the difference between your bust and your band, so the physical size of the cup depends on the band it is cut onto.
Run the numbers. A 38B is built for a bust of 39 to 40 inches. A 30B is built for a bust of 31 to 32. Both are labelled B, and the cups are nothing like each other. The letter has told you how much bigger the bust is than the band, and nothing about how much there is.
So comparing cup letters across people is meaningless unless the bands match, and a 38B is a larger garment than plenty of sizes with scarier-looking letters.
Is 36B or 38B bigger?
38B, in both the band and the cup.
The band is two inches wider, which is obvious. The cup is bigger too, because each letter is measured against its own band, so the B on a 38 holds more than the B on a 36. A larger band with the same letter always means a larger cup.
If you need the extra band width without the extra cup, the size to ask for is 38A, not 38B.
Is 38B or 38C bigger?
38C, by about an inch of difference between bust and band. Same band, one letter up.
They feel identical around the ribcage, so this is the easy adjustment. If the band is comfortable but the cup edge cuts in or you are spilling at the underarm, 38C is the direct fix. If the band itself is the problem, changing the letter will do nothing at all.
Shop the band first
On a wide band the band is doing most of the work, and a loose one fails visibly: it rides up your back, the straps take over, and your shoulders take the load.
The check takes five seconds. Fasten the bra on the loosest hook and pull the band away from your back. More than about an inch of give and it is too loose. A new bra should fit on the loosest hook so the tighter ones are there as it stretches with wear.
If your band is right and the cup is wrong, change the letter. If the band is wrong, change the band, then correct the letter to match. Doing it the other way round is how people end up in a 40B that fits nowhere.
Sister sizes when 38B is close but wrong
Move the band one step and the letter the opposite way:
40A ← 38B → 36C
All three hold a similar volume and differ in how tightly the band sits.
- Band rides up at the back, cup fits: go down to 36C
- Band comfortable, spilling over: stay on 38 and go up to 38C
- Band digs in or leaves marks, cup fits: go up to 40A
The first of those is the most common by a distance. A band that has crept up between your shoulder blades by evening is the single clearest sign you are in the wrong band, and going down one while going up a letter keeps the cup where it is. How that trade plays out at every other size is in our sister sizes guide.
When the outfit takes the band away
The wider the band, the more it shows under fitted clothing, and the more likely a neckline is to remove it entirely. Backless blouses, halter necks, deep V necklines and low saree drapes all do.
What holds without a band:
- A strapless adhesive bra in your cup size, which sticks to skin and keeps its shape with no band and no straps. It is made in 38B.
- Lift tape, positioned by hand, for necklines a moulded cup cannot follow.
If tape has failed you before, it is usually skin preparation rather than the tape. Our post on what goes wrong covers the mistakes that cause it to lift.
The short version
A 38B fits an underbust of 33 to 34 inches with a bust an inch or two larger. The letter reads small and is not: a B on a 38 band is a bigger cup than a B on any narrower band, because a letter is a difference rather than a volume. Shop the band first, then correct the letter.
The full method is in our bra size chart for India, and the same letter on a narrower band is covered in 36B bra size. The 38 bra size guide takes the whole band at once, 38A to 38D.
