How to sew a bra muslin

Making a muslin or test version of your bra is a crucial step in creating a well-fitting bra. Today, we’re showing you how to make a bra muslin.

Jump to another post in this series:

Bra fitting guide overview
How to choose your bra size
How to make a test bra
How to adjust the back band
How to adjust the gore/bridge (Willowdale only)
How to adjust the cups
How to adjust the center insert (Loftus only)
How to adjust the side seam angle
How to adjust the straps
How to adjust the underwires (Willowdale only)
Adjusting the level of support and comfort
How to make an asymmetrical bra
Additional bra making resources

Cashmerette has two bra patterns designed to support and lift big boobs in band sizes 28-54 and cups C-J, all while looking absolutely fabulous! The Willowdale is a full frame, underwire bra sewing pattern while the Loftus is a non-underwire bralette sewing pattern.

Get the Willowdale Bra pattern

Get the Loftus Bralette pattern

Start your bra fitting journey with the Cashmerette Bra Fitting Guide

To help you sew and fit your dream bra, we’ve put together the Cashmerette Bra Fitting Guide! This post is one of the many tutorials you’ll find there, and if you haven’t yet checked out the main guide page, we recommend starting there. So much of bra fitting is interconnected, and the guide provides a checklist and order to work through the adjustments.

Check out the Bra Fitting Guide

In this post, we’re covering how to make a muslin. Let’s get started!

What is a bra muslin?

A muslin, also known as a toile, is a test version of the garment you’re making. It’s important to make a muslin for every new pattern you try, but this is even more true when it comes to bras.

Our bodies (and boobs!) come in all shapes and sizes, and we rely on our bras to fit well and provide the support we need without hurting in the process. It can take a few tries before you perfect your bra fit and you don’t want to cut into your precious final fabric until you know you have a version of the pattern that will fit you beautifully.

What fabric should I use for a bra muslin?

You might think that you should use muslin fabric to make your bra muslin—nope!

Bra fabric comes in all weights and stretch percentages, and both of these factors can impact how the bra fits you. So the best way to determine how your final bra will fit is to simulate it with fabric that is as close as possible to your final fabric. If possible, buy extra fabric and make your muslin with the exact same fabric!

The Willowdale Bra is designed for low stretch fabrics of up to 20% stretch. It relies on this stretch to accommodate differences in bra shapes and to get a good fit. You can make it with non-stretch fabric or fabric with a greater stretch percentage, but you may need to spend more time working on the fit if you do.

The Loftus is designed for non-stretch to low-stretch fabrics with the non-stretch cup lining. You can make it with a fabric with more stretch but it will not provide as much support.

As for the rest of the bits and bobs—the stretch lace for the upper cup on the Willowdale, the power mesh for the back and powerbar, and the band, underarm, neckline, and strap elastics—you should use ones that are as close as possible to your final materials as well.

How do I make a bra muslin?

You may not want to hear it, but here’s the hard truth: when making your bra muslin, you’ll need to sew up the entire bra. Bras are designed with tension that goes in all different directions, and it’s nearly impossible to determine how a bra will fit without all of the tensions coming into play.

Some bra makers recommend making a single cup to check the cup volume, but it’s difficult to use this technique to get a true sense of the cup fit and it won’t tell you much about how the rest of the bra will fit. At the end of the day, the best approach is to sew up the entire bra.

But that said, you can take some shortcuts to save on time and materials:

For the Willowdale Bra

You can make View A which has a solid body and stretch lace only on the upper cup
You can baste all your seams and underwire channeling
You can baste your elastic (using a longer zigzag or stretch stitch) and hardware to make them easier to remove and reuse
You can skip adding the lingerie bow
Do not sew any of the bar tacks that hold the underwires in place
You can use mismatching elastic, notions, and thread to use up leftovers from other projects (assuming they’re all similar to your final materials), or harvest materials from old bras

For the Loftus Bralette

You can baste all your seams
Do not top stitch any of the seams – especially the center front of the center insert.
You can baste your elastic (using a longer zigzag or stretch stitch) and hardware to make them easier to remove and reuse
You can use mismatching elastic, notions, and thread to use up leftovers from other projects (assuming they’re all similar to your final materials), or harvest materials from old bras
Make only the lining, powerbar and center insert, do not add the main fabric (unless you need to test how it will work due to stretch, etc.)

Ultimately, bra fitting is not a quick endeavor, and making a muslin is just part of the process. But you’ll be happy that you took the time to do it right, and you’ll end up with a much better result! Plus you’ll have gotten to practice the techniques and construction along the way which is never a waste of time.

How to make a bra fitting sample

If you’ve made one or more bras before and feel comfortable with the bra-making process, here is a more advanced way to make a bra muslin. This method, shown below by Jennifer of Porcelynne using the Willowdale Bra, allows you to construct the different sections of the bra separately and puts them all together at the very end, which means you can swap them out and make adjustments without having to sew up a whole new bra muslin.

Keep in mind that this construction method is not the same as the construction used in the pattern’s instructions.

This technique is not recommended if it’s your first time sewing a bra.

I’ve made my muslin. Now what?

Congratulations! This is an important first step in the bra fitting process. The next step is to evaluate the fit and make plans to refine it. Head to our Bra Fitting Guide to learn more!

Check out the Bra Fitting Guide