Jul 07, 2025

How to Measure Your Bra Size for a Plus Size or Large Bust (UK Guide)

by Orchid Fashion Boutique

If you've got a fuller bust, you've probably noticed that generic "how to measure your bra size" guides don't quite cut it. Standard advice assumes a fairly average band-to-cup ratio, but once you're moving into D, DD, E cups and beyond, the maths and the fit issues change. Here's how to measure properly for a plus size or large bust, and what to do with the result.

In short: measure snugly under your bust for your band size, then around the fullest part of your bust for your cup size. For larger busts, pay extra attention to band fit first; an oversized band is the most common cause of discomfort, and getting it right makes everything else (strap dig, underwire poking, cups gaping or spilling) fall into place.

Why measuring matters more for a larger bust

The heavier your bust, the more work your band does. Roughly 80% of a bra's support should come from the band, not the straps, so if your band is too big, your shoulders end up carrying weight they were never designed for, leading to deep strap marks, neck and back ache, and a band that rides up at the back.

For a larger bust, getting the band size right first, then fine-tuning the cup, makes a much bigger difference to comfort than it does for smaller sizes, where a slightly loose band is less noticeable.

How to measure your bra size step by step

Step 1: measure your band size

Wearing a non-padded bra (or no bra), wrap a soft tape measure snugly around your ribcage, directly under your bust. The tape should be level all the way round and firm enough to stay in place, but not digging in. Round to the nearest whole number in inches; this is your band size.

Step 2: measure your bust size

Wrap the tape around the fullest part of your bust, usually across the nipple line, keeping it level across your back. Don't pull it tight; it should sit comfortably without compressing.

Step 3: work out your cup size

Subtract your band measurement from your bust measurement. Each inch of difference corresponds to a cup size: 1" = A, 2" = B, 3" = C, 4" = D, 5" = DD/E, 6" = DDD/F, 7" = G, and so on. For a larger bust, don't be surprised if this calculation lands you in F, G, or even higher; that's completely normal and exactly what our Gemm range is designed for.

Common fit problems at larger sizes (and what they mean)

Straps digging into your shoulders: usually means the band is too big, so the straps are doing the job the band should be doing. Try going down a band size and up a cup size to keep the same overall volume.
Band rides up at the back: the band is too loose. Tighten to the next hook, or size down the band.
Cups gaping at the top or sides: the cup is too big for your shape. Try the same band with a smaller cup.
Breast tissue spilling over the top or sides: the cup is too small. Try the same band with a larger cup.
Underwire sitting on breast tissue rather than your ribcage: usually the cup is too small, the band too big, or both.

What about sister sizes?

If a bra feels almost right but not quite, sister sizing can help. Going up a band size and down a cup size (or vice versa) gives you a similar cup volume in a different band/cup combination, for example 38D and 40C hold a similar volume. This is especially useful when shopping online and a specific size is out of stock, or when one brand's fit runs differently to another's.

Choosing the right style once you know your size

Once you've got your measurements, the right style matters just as much as the right size. For everyday wear, look for wide, cushioned straps and a full cup that fully encloses the breast without cutting in. Our full cup bras are designed with larger busts in mind, with reinforced support and sizes up to 46J.

If you're between sizes or simply prefer non-wired comfort, our front fastening bras offer a forgiving, stretch-cotton fit that's easy to adjust and even easier to put on.

Frequently asked questions

How do I know if my bra band is too big?

If the band rides up at the back, or your shoulder straps are digging in and leaving marks, your band is likely too big. Try sizing down the band and going up a cup size to maintain the same overall fit.

What's a sister size and how do I use it?

A sister size is an alternative band/cup combination that holds roughly the same cup volume, for example 36DD and 38D. If your usual size is out of stock or doesn't fit quite right, try the sister size up or down.

How often should I remeasure my bra size?

It's worth remeasuring at least once a year, or any time you notice a significant change in weight, after pregnancy or breastfeeding, or if your current bras suddenly feel different.

I measure into a G cup or higher; will Orchid have my size?

Yes. Our range is specifically designed for fuller busts and plus sizes, with bras available up to 46J and band sizes up to 48, depending on style.

Can I measure accurately without help?

Yes, though a mirror helps to check the tape is level. If you can, ask someone to help check the back of the tape is sitting straight and not riding up.

Shop our full range of plus size and full cup bras, designed for comfort and support up to 46J, with fast UK delivery and easy 30-day returns.