But the bra retailer insists on adding 5 inches

[MiserableAsSin]

Bra fitting problem .
Delighted that Boux Avenue are making bras with a 28inch band .
On their website they ha e a bra fitting tutorial video which advises you to add on the 5 inches ( they have a model with a 26.5 inch under bust and correspond that to a 32 inch bra )
So technically , I have a 27 inch under bust measurement and should be wearing a 32 inch bra .
It's confusing . They size up, design and manufacture their own bras. Surely they would know if the 5 inches need adding or not . But this goes against every real bra fitting advice I've read which states don't add on the five inches . I'm pretty small - a size 6-8. Can't imagine many women having a 23 inch under bust measurement , to require their 28 inch bra . But it also seems equally incredulous , that bra manufacturers haven't tested and designed their own bras properly.
Which way is right ?

Never add the extra inches! Your actual measurement is your actual bra back measurement.

I thought so too but it's such a mystery to me why retailers insist on adding them . Don't they factor all this in at the design stage ? Aren't their bras tried and tested on real women ?

@Tippexy is spot on. What you measure is what size band you need. I've heard this add five inches rubbish for years. I get measured once a year at Bravissimo, and have done for many years. They won't even use a tape measure to tell you your size. They sell their own make and well known brands, all of which have been an exact fit to the size they have measured me at.

I get you OP. I would love to see what their target women are for their 28 inch bras. So ridiculous. Like you say, I wonder do they not road test their sizing. It’s baffling. I’m a 28 too, and a 32 or 34 would be up around my neck.

you would think they know, but M&S fitting tutorial also had a model with 1 inch underbust and the 'expert' decided she needs a 36 bra..