Adjusting a bra pattern for foam cups

lingerie Jan 20, 2021
sew foam cups

Sewing bra’s with cut and sew foam can be a bit intimidating. One, maybe you don’t know how to sew the foam. Two, maybe you don’t know how to adjust your bra pattern for adding foam cups.

If you have a great bra pattern that doesn’t come with instructions for adding foam cups, don't worry. You can draw the pattern yourself. Actually, it's very easy. I’ll show you how to adjust a bra pattern for foam cups in this blogpost.

So take your favourite bra pattern, some tracing paper, pencil and rulers and some foam and let’s get to it!

! To be clear, this blogpost is about cut and sew foam, not moulded cups.

! Another remark: adding the cut and sew foam can result in a tight fit. If the pattern is not constructed for foam cups, I always go up 1 cup size. Only in cup size, not in band size!
Or you can measure yourself while wearing a bra with foam cups (instead of a bra without foam) and use these measurements to determine your size. In this case, you won’t need to size up.


First, choose how you will finish the edge of the cups

To adjust your pattern, you will need to know first how you will finish the edge. You will need to stabilize it with elastics or a binding.

I will show you 2 easy ways to finish your foam edges.

Foldover elastic

The easiest way in my opinion is to sew foldover elastic (FOE) over the foam and fabric. For this method, you will take the cup in fabric and place it with the wrong side on the foam cup. How you place them on each other is also how you will wear the cups. You take the FOE, fold it over the top edge of the cup and sew it with a zigzag stitch. Easy peasy!

There are no extra seam allowances needed here on the upper edge of your fabric and foam upper cup pieces.

Main fabric

If you don’t like the look of FOE and only want to see your main fabric, you'll need to sew the fabric on the foam from the inside and then flip it over.

The foam is too thick, to sew fabric and foam with right sides together and turn inside out. Instead, sew the fabric with the right side against the inside of the foam. For extra stability you can even sew an elastic in this seam.

Flip the fabric over to the other side and pin lower edges of fabric and foam cup together.

There are different kinds of quality in cut and sew foam. Some are very flimsy and need an extra elastic. The cut and sew foam that I use here doesn’t need it.

For this method you will need 1 cm seam allowance on the upper edge of your FABRIC (not your foam!) upper cup piece. The 1 cm is 5 mm of seam allowance and another 5 mm to turn the fabric over that seam allowance. If you have a very stretchy fabric, you can use a 5 mm seam allowance there.

1 cm of seam allowance on the top edge of this FABRIC pattern piece

Drawing the foam pattern pieces

You take your cup pattern pieces. Let’s take this example of the Boylston bra from Orange Lingerie. I have an upper cup, and inner lower cup and side lower cup. You need the pieces without seam allowance or have the seam allowance clearly indicated on your pattern pieces.

The foam pieces will be sewn together without seam allowance but against each other with a zigzag stitch. So everywhere you will sew the foam pieces to each other, you have to omit the seam allowance. (arrows in blue)

You do need to sew your foam cups into the cradle, so keep (or add) the seam allowance of 5mm on all the edges that get sewn into the cradle.

(arrows in green show where you add seam allowance)

If you’re going to finish your upper edge with foldover elastic, you use the upper cup pattern piece without a seam allowance there.
If you want to cover the edge with fabric, you add the 1 cm seam allowance on the fabric upper cup and leave the foam upper cup without seam allowance on the upper edge.

Et voila, now you know how to draw your pattern pieces and can sew your favourite bra WITH foam cups. If you would find it helpful, I can also do a blogpost on how to sew the foam cups. Let me know in the comments or via social media if you would like that.

If you want to try out a new pattern for your next project have a look at my patterns page!

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