To Get the Right Armhole, Fit the Bodice
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There’s more to fitting an armhole, also known as an armscye, than you may think-it requires fitting the bust dart, shoulders, and side seams. And the only way I know to successfully fit an armhole is to use a muslin. For more information on armhole fittings be sure to pick up Threads #117, and don’t miss other techniques like this one by ordering a print subscription which comes with FREE access to our tablet editions.
People with identical bust and over-bust measurements often fit into the same size and style pattern differently (see Same measurements, very different figures). The shape of your body depends on where you carry your flesh and dictates the shape of an armhole. A muslin is the testing ground-it’s the perfect place to sort out fit issues.
Same measurements, very different figures
A muslin is a test garment in inexpensive fabric, initially sewn without facings or edge finishes. You pin-fit the muslin right on the body. The object is to make the fabric skim the body with no signs of wrinkles or strain lines. Although becoming a fitting expert can take years of practice, I’m going to give you a straightforward method of how to fit an armhole and develop a well-fitting bodice muslin that accurately reflects the shape of the body.
Follow this order when fitting: bust, back, underarm, shoulder seam placement and slope, shoulder point to underarm, and side seams. Then adjust the pattern tissue using the fitted muslin as your guide. Such a completed pattern can be used as a reference to position darts and establish the armhole shape in future patterns. You’ll end up with a perfect pattern for a closely-fitting bodice with or without set-in fitted sleeves. Just because fitting can be complicated, don’t let it scare you away.
Use this glossary to help navigate your pattern and understand the fitting process and the terms used in this article. Key landmarks are identified on these pattern pieces. The dotted lines indicate possible fitting sites.
You’ll need a person, a pattern, and some woven fabric
Don’t try to fit a too-small pattern. A strain between bust points means you need a larger pattern. See Choose the Correct Pattern Size.
Select a fitted blouse pattern intended for woven fabrics that includes bust darts in the side seam or armscye. (See above Glossary of terms for an overview of the pattern areas that will be need adjustment.) Make sure the finished bust measurement printed on the pattern is between 1-1/2 and 2-1/2 inches greater than your actual full bust measurement to allow enough wearing ease (wearing ease is the difference between your body’s measurements and the finished garment’s measurements, which is necessary so you can move in the garment). Use a stable woven fabric without spandex, and follow the pattern to make your sleeveless, collarless muslin. Sew your seams using a long machine stitch, and use a thread color that contrasts with the muslin fabric so that you can easily see to clip and release seams during fitting .
You’ll need an assistant for the fitting process. Consider hiring a dressmaker to help you. Plan on making several muslins to get the right fit; the results are well worth the effort. If you’ve never made a one, watch this video to learn how to make and and use a muslin.
A muslin tells you more than your measurements alone do
The first muslin serves as the rough draft for blocking out the major fitting changes. I always make at least one additional muslin to check my first fitting results. If you’re a beginner, it’s better to make more muslins with fewer changes to each than to try too many changes at once.
Don’t try fitting a muslin that’s a size too small because the tightness distorts the overall fit. For example, if you get a strain line between the bust points (drawing above right), start over using a larger size pattern.
It’s important to make sure the bodice stays level around the body and doesn’t dip in the front or back during the fitting. I draw a horizontal balance line (HBL), on the face of the muslin so I have a point of reference that I can easily see while fitting (drawing below left). I often use the lengthen/shorten line (between the waist and underarm rather than at the hem) as my HBL. While fitting, periodically check the level on the front and back HBL. If the back HBL dips, pin a wedge out of the upper back to level the line.
Use horizontal balance line (HBL) to help you keep your pattern level.
If your side seams strain, open them over the problem area.
Stand back and read the muslin to assess the fit
To get started, study the general fit of the muslin and make any obvious adjustments. If the side seam strains over the hip, open both side seams from the hem upwards until the muslin falls nicely (drawing above right). If the shoulder seam is too loose, pin out the excess fabric. The muslin should fit without strain but not loose and baggy. Remember, to get a pattern that reflects the shape of the body, you’ll want to develop a fitting muslin that fits like a second skin-snug but not tight. Add design and additional wearing ease later.
Most often fit only one side of the muslin after making the HBL level. If the person is particularly asymmetrical, over-fitting can actually accentuate an uneven body. In general, if one side of the bust is larger, fit the larger side; if one shoulder is higher, fit the higher side, and adjust the low shoulder with a pad.
Assess how the muslin fits at the bust
Ease excess fabric to form darts.
Darts contour the fabric to accommodate the swell of the bust while keeping the garment looking trim. Anyone with a full A-cup or larger benefits from properly placed bust darts, which make the center front of the garment fall straight to the waist and not swing away from the body. This results in a more flattering silhouette. The correct bust dart also keeps the armhole from gaping.
Some women carry bust tissue under their arms, other women carry it in front. Experiment with positioning the angle of the dart until it’s most flattering. The dart placement alone can visually slenderize the figure.
I prefer to use side darts in a base pattern such as this, but pinching out a dart in the armscye to eliminate the gape and then moving the dart to a better location later is a good approach. Read the muslin and use your fingers to ease up any dragline-in this case, a diagonal fold of fabric occurs between the bust apex and the side seam-into the side bust dart.
The way you drape a bust dart influences how it flatters the body. Use the dart as a design element that directs the eye to your advantage.
Set the point of a dart closer to the apex for a smaller bust, farther away for a full bust. Don’t be surprised if your dart seems larger than usual as long as you’re getting a smooth fit. A very large dart may be needed to fit a very full bust. If this causes an unattractive bubble at the dart-point, two parallel darts will solve the problem. Pin in the required dart(s) that best fit the bust.
Raise the depth of the armhole.
Increasing the size of a side-seam dart lowers the front armhole. Fill the vacancy with a small piece of fabric to bring it up to the original height and redraw the armhole seamline.
Stand back and evaluate whether the dart-point hits in a pleasing place on the bust. If the dart’s too low, it looks matronly, and if the dart’s too high, it can look unflattering as well. The way you drape the dart influences how it flatters the body. Decide whether a slanting or straight dart fits you best.
Dart corrections on the back shouldn’t end in the armhole
Now that you’ve adjusted the bodice front, check the back for excess fabric or undue strain at any point and assess the fit in the same way you did on the front. If the back armhole gapes, release the side seam and push the side back toward the front to diminish the gape and redraw the side seam.
If the back armhole gapes, reposition the side seam.
Add princess seams and a center back seam to accommodate extra back curvature.
If there is considerable roundness in the back, adding darts at the shoulder seams or even adding a center-back seam for extra curvature is a good solution. If an armscye dart is needed to fit a muscular back, incorporate the dart amount in a princess line (back armscye darts are not traditionally used). The object is always to reduce any excess fabric in the circumference of the armscye.
Most patterns are cut too low under the arm
Now that you’ve draped darts to match your curves and removed excess fabric from the back of your muslin, the shape of your armhole has probably changed. Deciding where the armhole hits under the arm is partially personal preference. Remember that an armhole cut high up under the arm is generally more comfortable because it allows a greater range of movement in a garment with sleeves; this is often counter-intuitive to a beginning fitter. A sleeveless garment is only 1/2 inch higher under the arm than a fitted garment with a sleeve.
If the armhole is cut too low under the arm, add a piece of fabric and draw in a new depth; or make a note to raise the underarm a specified amount on your pattern tissue. If you hold a ruler under your arm as high as is comfortably possible, the underarm seamline should fall barely below where the ruler is touching the flesh.
Center the shoulder seam and correct the slope. From the shoulder point follow the body curvature and draw a new armhole.
Check the shoulder point and side seam
Changing your shoulder seam is a judgment call. The seam should lie along the top of the shoulder at a place that balances the body front to back and follows the natural slope of the shoulder. The shoulder point falls on the shoulder seam at the exact place the arm and shoulder come together-at the dent that forms when you lift your arm.
On the muslin, draw a line that falls from the shoulder point to the “crook” of the arm (where the arm attaches to the body) and then runs under the arm at the “break of the arm” (where the curve begins to go under the arm). Draw the curvature of the armhole on the muslin to follow the body curvature from the shoulder around the arm on both the front and the back.
Check that the side seam hangs straight. Make adjustments by releasing and repinning the seam so that it’s perpendicular to the floor. Assess if it divides the side of the body attractively.
Transfer the muslin alterations to the pattern
Mark the seam and dart lines directly on the muslin, and follow any instructions noted on the muslin during the fitting. Use a permanent marker and always mark and concentrate on the actual seamlines. To reduce confusion, ignore seam allowances until later. The muslin is now a road map of the changes needed on the pattern.
Make a working record of all your adjustments
Go back to your original pattern and transfer the muslin corrections to the tissue. I don’t use the muslin as a pattern because fabric molds to the wearer’s body and stretches with cuts across grainlines. Plus, it’s easier and more reliable to walk and true seamlines in paper because paper doesn’t stretch or distort.
How to walk and true a seam
In the course of adding darts and making other fitting adjustments you have also made multiple changes to the seams. Now you have to determine that both sides of a seam are the same length-to do this we walk and true the seam.
To walk the seams on your paper pattern, first pin in the darts and then compare the stitch lines of adjacent seams (side front to side back, or shoulder front to shoulder back) in 1-inch increments from one end of the seam to the other. If the seams aren’t the same length, use the HBL, notches, and key landmarks to determine where length should be added or subtracted. It is essential to compare actual seamlines excluding the seam allowance; the seamlines must match in length to enable precise construction.
After walking the seam, true it by using a fashion rule or French curve to blend any jagged seamlines (that formed during the alteration process) by drawing a new smooth line to bridge the gap. If you’re unsure what the ideal blending line is, it’s safe to split the difference between two lines-and remember, you’re making another muslin and have another opportunity to fine-tune the fit and seamlines again.
Once the changes are made to your pattern, it may look substantially different from the original-especially in the front armhole. On a large bust, the armhole might now have an “L” shape. We’re accustomed to seeing a long gradual curve on commercial patterns, but that isn’t the shape many of us need.
Concentrating on the stitching lines, add new tissue to your pattern where it’s needed. Pin in the new darts and walk the corresponding seams as described in How to walk and true a seam.
Clip to the stay-stitching around the armhole to enable armhole fit assessment.
After the seamlines have been corrected and trued, draw and cut the new seam allowance while the darts are folded so the correct dart legs automatically form.
Now make your second muslin. This time staystitch the armhole seams. The armhole is much higher now and you’ll probably need to clip the curves to the staystitching for a comfortable fitting. The new armhole curve should not be tight but should just skim the body.
The second muslin will most likely require few dramatic changes. Follow the same steps as before, this time fine-tuning the fit and the position of the seamlines.
Sarah Veblen teaches, designs, and sews from her studio in Sparks, Maryland.
Drawings, except where noted: Deb Bassino
Fitting an armhole requires fitting the bust dart, shoulders, and side seams.