How to Sew a Muslin & Assess Fit!

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Hey, you!

Writers write rough drafts. Professional chefs cook test recipes. And athletes practice to increase their skills and perfect their game.

And if this is your first time sewing any pattern, yes, you absolutely should sew a test garment, a muslin.

Muslins get a lot of hate, but…

I love sewing muslins!

Yes, you read right: I love sewing muslins!

And here’s the many reasons why…

NOTE: If you’re ready to begin this journey and would like to buy my recommended tools and supplies, please click HERE!

You Should Love Muslins Too!

  • You may find errors in the pattern. Yep, it happens. And I have.
  • You can make certain that the style will be flattering to you. This is how you “try on” a sewing pattern.
  • You can adjust the amount of ease to your liking.
  • You can determine your personalized fitting issues and refine the fit. This is of particular importance for fitted or semi-fitted silhouettes.
  • You can practice new or tricky techniques. For example, you don’t want to be installing a zipper for the first time with your fashion fabric. Ask me how I know this?!

  • You can check the pocket and button placement.
  • You can check the neckline modesty level.

And what is really glorious about making a test garment…

  • You can save both money and time in the long run. Because once you find a pattern you love and you’ve fitted it to your liking, you now have a tried-and-true (TNT) pattern that you can play with and yield an infinite number of dresses simply by changing the fabric and style details!

Now, how awesome is that?!

Okay, I hope that I’ve convinced you of the beauty of sewing a muslin. Now, let’s learn how to do just that…

Two Key Tips to Sewing Muslins


Before you learn how to sew a muslin, I need to share two things with you:

  • Your muslin can be the actual unbleached, cotton muslin fabric as pictured above. Yep, you sew a muslin with muslin fabric. Or, it can be an inexpensive fabric that has a similar weight and drape as your fashion fabric.
  • Treat your muslin as if it is an exquisite length of the most luscious fabric that you’ve just shelled out $50/yard for.

UPDATE: Since publishing this article, I’ve worked extensively with muslin fabric, and  I’ve come to this conclusion…

I despise how it looks, how it feels, and how it drapes! Therefore, going forward, I will be using inexpensive fashion fabric for my sample garments.

Alright, it’s time to learn how to sew a muslin, step-by-step…

How to Prep Your Muslin


Now, here’s the great thing…

A muslin is easy to sew. You only need to cut out the main pieces of the garment, such as the bodice front, bodice back and sleeves. No facings. No pockets. No hem.

And here’s how you do it…

ONE, gather your supplies:

TWO, choose your starting pattern size.

THREE, set aside the main pattern pieces. For a top or dress that would be the FRONT and BACK of the garment and the sleeve. And for a skirt, FRONT and BACK of the skirt.

For example, in the image below,  you would set aside pattern pieces #1, #4, and #5. These are the three pieces you must sew a muslin for to check the fit around the neckline, armhole, and bustline.


FOUR, press your tissue pattern pieces with a dry iron on the WOOL setting to remove all folds and creases.

Trace a copy of your sewing pattern if you wish and extend the grainline along the entire length of the pattern piece (see the blue arrows in the image below)…


Go ahead and remove the hem allowance from your traced pattern. You can also choose to fold it up when fitting.

FIVE, straighten the grain of the muslin fabric, and then…

Layout & Pin

Layout and pin your main pattern pieces on the muslin.

And with a seam gauge, add 3/8 inch to the 5/8 inch seam allowance (SA) to make 1″ SA at the side seams (SS) and the shoulder seams. This should give you plenty of room to make adjustments if you need to.

In the image below, I’ve added 3/8 inch to the cut edge. This is called fit insurance (see the blue arrow below).

Sew easy tip: If you are using actual muslin, you do NOT have to pre-wash your muslin fabric!

Now, you’re ready to…

Cut & Mark

Cut out the pattern pieces.

Snip the center front (CF) at neckline and at the hem if it is not defined by a seam.

Mark or snip dart legs, notches, and zipper stop.

Mark the dart points.

Mark the wrong side (WS) of the muslin with an X.

Remove tissue pattern and on the right side (RS) of the muslin. With your grid ruler and blue, fine point marker, mark the horizontal balance lines (HBLs)…

  • at the chest ~ notch to notch, notch to CF, or notch to center back (CB)
  • at the waistline ~ side seam to CF or side seam to CB (you can use the waistline marked on the pattern)
  • at the hip line ~ side seam to CF or side seam to CB (you can use the hip line marked on the pattern)

Then, draw in the dart lines and seam lines with a blue, fine point marker.

Repeat the above on the BACK pattern piece.

This is how you would mark a sleeve pattern piece…


And for a skirt pattern piece, you would mark the horizontal balance line at center front (CF) or center back (CB) and at the hip line. See the image below for an example of ALL the horizontal balance lines…


I’ve listed excellent fitting resources, such as books and fitting patterns, in What You Need to Know to Fit a Sewing Pattern that can help you with this entire process. Choose ONE to get started.

Alright, remove the tissue pattern and you’re ready to put this baby together…

How to Sew Your Muslin

What you’ll need in addition: an all-purpose zipper.

You’ll be machine basting your muslin pieces together. I like to use a 4mm stitch length. Anymore than that, and I’ve found that the muslin begins to unravel faster than you can say, “He’s a cold-hearted snake!”

Also, I backstitch at the start and the end of my stitching lines for the same reason. And I haven’t found unpicking these stitches to be difficult!

Alright. Let’s do this…

ONE, staystitch the neckline and armholes directly on the SEAM line.

And then, trim off the SAs right up and close to the line of staystitching at the neckline and the armhole like this…


This way you can accurately assess the fit at the neckline and the armhole without seam allowances getting in the way.

TWO, sew all darts to the RS or the outside of the garment; press dart bulk downwards. Sewing the darts to the RS will allow you to adjust the size of your darts more easily.


THREE, sew the CB seam and insert a centered (slot) zipper if applicable and press.

FOUR, now it’s time to put our main pieces together.

If this is a dress or a bodice, sew the FRONT and the BACK pattern pieces wrong sides together (WST) at the shoulder seams so that the SAs of the shoulder seams are also on the RS or the outside of the garment. This will allow you to adjust the shoulder slope more easily.

If it is a skirt, you’ll be pin fitting the SS.

Then, press the SAs open. Yes, you must still press!


FIVE, now, with WST, try on your dress, bodice, or skirt and pin fit the side seams (SS) to the contours of your body.

In other words, leave the SS of your dress or bodice unsewn and pin fit them to the shape of your body.

Place the straight pins with the sharp points downward! Once again the SAs will be the to the RS or outside of the garment for easier adjusting.


Just make sure your use Dritz Extra-Fine Glass-Head Pins (White or Blue Pinhead)!

When that’s done, press the pin basted seams!

Yes, you have to press your pin basted seams if you’re to assess fit accurately!

Sew easy tip #1: Instead of machine basting the darts, shoulder seams, and side seams, you could pin baste everything. Try both and see which you prefer. Or, maybe like me, you prefer a combination of both.

Sew easy tip #2: If the dress (or bodice) will have sleeves, always fit sleeves after you’ve adjusted the fit of the main garment at SS.

That’s it!

Get your red, fine point marker ready! You’re now ready to assess and adjust the fit

How to Assess Fit

Now, that your muslin is basted together, you’re ready to assess the fit.

What you’ll need:

  • ¼-inch wide elastic;
  • full-length mirror;
  • hand mirror;
  • red, fine point marker;
  • patience; and
  • confidence.

Try on your muslin with right side out. Because we wear our garments right side (RS) out, it is important that we assess it that way, especially if we have any asymmetries.

When assessing fit, you are looking for two things:

  • areas that look and/feel too big (gaping and sagging); or
  • areas that look and/feel too small (pulling, straining, pinching, and binding)

All you need to do as you make your adjustments is to pin out excess fabric and use your red pen to mark the new stitching line along the line of pins.

Or, slash where it is too tight and measure how much it spreads.

In other words, use your muslin to pin fabric accurately to your curves and contours of your body until you get the fit you want.

Horizontal Balance Lines (HBLs)

You will also be using the HBLs you marked earlier to make sure that the garment is hanging from your shoulders or waist on grain. That is, you want to make sure that the HBLs are parallel to the floor across their full width!

Because a good fit is never lopsided!


Order of Fit Assessment

You need to assess fit in this order:

Start at the back and at the top. In other words, check the fit at the upper back FIRST, and then the shoulder slope.

Because if you have a broad or rounded back or protruding shoulder blades, the front will NOT fit until you fit the back properly.

And since garments hang from our shoulders, the shoulder slope has to be right before you can accurately assess the rest of the garment.

To begin assessing…

FIRST, tie a length of ¼-inch wide elastic around your waist. And then, stand in front of a full-length mirror.

Make sure you are looking straight ahead. Because turning distorts the fit of the garment! So when you’re assessing the back, use a hand-held mirror.

SECOND, you need to assess fit first from the BACK, and then the FRONT.

Ask yourself the following questions:

  • How is the fit at the upper back?
  • Is the shoulder slope correct for your body? And are the shoulder seams smack dab in the middle of your shoulders and in line with your ears?
  • Check the lengths: Are the bustline, waistline, and hip line in the right places on your body?
  • Check the widths at the bust, waist, and hip: Is the garment comfortable to wear? Is the amount of ease to your liking?

The width of a garment consists of the body measurements for bust, waist, or hips plus ease.

  • Is there any straining or pulling around the zipper or buttons and buttonholes?
  • Are the darts pointed in the right direction? And do they end at least ½ to 1 inch away from the curve they are shaping?
  • Do the neckline and armholes lie flat without gaping or binding?
  • Does the bodice fall smoothly across the upper back and chest to below the armholes?
  • Are all side seams (SS) perpendicular to the floor?
  • Is the hemline the same distance from the floor all the way around?
  • Finally, how does it feel to stroll around; bend over; sit down; cross your legs; reach forward; and reach way up?

Sew easy tip: Do NOT overfit! That means, do not remove minimum wearing ease — 2 to 3 inches at the bust; 1 inch at the waist, and 2 to 4 inches at the hips — unless you enjoy walking like a mummy and being unable to sit, breathe, or eat!

The End

That’s it! That’s a lot! And honestly, that’s only the beginning!

Assessing fit is both an art and a science! In other words, along with the wealth of fit tips I provided HERE, you will need to trust your gut when assessing fit!

But there’s good news…

You only need to worry about fit for garments that are fitted or close-fitting!

Plus, if you’ve taken accurate body measurements; chosen your starting pattern size; made basic pattern alterations; and sewed a muslin,  then…

You may very well be in possession of a tried-and-true (TNT) pattern that you can use over and over and over again to make an almost infinite amount of styles by just varying your fabric choice and playing with style lines.

And I guess what?!

You’re now ready to layout, cut, and mark your pattern on your fashion fabric!

And remember…

Life is the ultimate red carpet event. Dress for it!

RELATED: Click HERE if you’re ready to unleash your dressmaking superpowers and learn how to sew a simple dress! Warning: This is a MEGA 5-part series!

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