How to Measure for a Bra

I often wonder why people find it so difficult to measure for your bra size. There is a simple formula, but the downfall is that if you are wearing the wrong size bra initially, the measurements will be wrong. Let me explain.

When we wear the proper bra, our bust sits so the bust point (very nice way to say nipple) at the center of our breast. If you are wearing a cup size too small or a cup that stretches too much, you will have “droopy boobs.” When the breasts are droopy, the bust measurement will measure smaller than it should.

This is also the problem is you are wearing the wrong size band. The band will make everything sit lower on the body, hence wrong measurements.

For my sew-a-longs, you can refer to these sizing charts (please note that the bras in my book might be off and I will be working on updating them by the end of the year). These directions work for most American brand bras and will also work for my 3 piece cup bra.

The Band Size

Once you have the correct band size, then you can start trying to figure out the cup size. But first, grab your tape measure and take two measurements. You want to take a snug measurement under your bust at the rib cage. Round to the nearest whole number. Write this down.

The second measurement you need to take is the over bust measurement. Also take this measurement snug. This is above all the breast tissue on the chest. Write this measurement down again rounding to the nearest whole number.

Refer to the following chart and use both the measurements you took to find your band size. If you prefer to just do the math, add the two numbers together and divide by 2. The nearest even number is your band size.

The Cup Size

The next measurement is the bust measurement. This amount will change as you may not be wearing the right size currently, but its a place to start. Try to measure over the bust point around the body.

You can use the following chart to compare the band size to the bust size and determine the cup size.

According to my sizes, I should be wearing a 36J. I cut all the pieces out for the cup in muslin. (You should be using a woven fabric for this pattern.)

All the bra pieces have 1/4″ seam allowance, so an easy way to figure out where 1/4″ sits on your sewing machine is to measure from the needle out on the foot to see where 1/4″ falls. On my machine, the 1/4″ is half way through my foot (mine has a big foot).

First you need to sew the top and bottom cup together. The notches should line up, but if they don’t, don’t stress about making them match perfectly.

Press the seam open. I used my fancy bra ham to iron around the curve. (And yes, I will be making these available as soon as I can figure out an inexpensive alternative to the wood block my husband had to cut out with his fancy tools).

Then sew the side cup to the pieces you already sewed together. Make sure that where you sew (at 1/4″) the seams meet up as pictured. Again, press after sewing.

I sewed a sample cup of the 36J in muslin and discovered it was slightly too big. I attribute this to not taking the bust measurement snug enough.

I then sewed the 36I, one size smaller and it fit really well. I also sewed underwire channeling onto the edge of the cup so I could see how it fit with the correct underwire. When I sewed the channeling, I just sewed it at 1/4″ from the edge of the muslin.

It fit much better!

Here is a sneak preview of the fabrics I’ll be using for the first bra sew along. I’ll put together kits of this fabric selection when I release my sew along so if you want the same custom made bra for yourself, you can have one. Happy fitting!

  1. The E on the chart translates to DD and the F translates to DDD. These are basic standard sizes, although many bra manufacturers don't use a standard chart, so you can vary slightly from brand to brand. Also different brands shape the bust differently as well. It really is up to one's own preference. One of the things I would like to do is create an app that translates one size from one manufacturer to a size of a different brand.


  2. Dear Porcelynne,
    I used your chart and got a 36F. I noticed your chart doesn't contain a DD, how do these sizes compare to regular American bra sizes? I wear a 36D or 36DD in American and UK cup sizes.
    Thank you.

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