Sometimes a garment fits well around the bust, waist and hips... but still seems a little off. The culprit could be the armhole or armscye.
Fitting the armhole can be the answer to a smooth-fitting and comfortable garment. Armhole adjustments involve a bit more intuition than exact measurements, but it is definitely worth the time.
Check for these 4 common fit issues & try these adjustments to get the perfect fit in your armscye.
Is the front armhole gaping? Add a dart.
Gaping at the front armhole can happen to anyone and any garment, but it's particularly common when you're full in the bust. If the lower third of the front armhole doesn't lay flat against the body, you can literally pinch out another dart to create a smooth front. So go ahead and pinch!
Pin out a dart as shown above, making sure the dart points to the apex. It should be a short dart — perhaps 2" long and pinching out anywhere from ¼" to 1" — since it's for fitting purposes only.
Mark the small dart on the pattern tissue or muslin, and then draw it in on your pattern piece.
Adding this dart will affect the other darts on your bodice (particularly a horizontal bust dart), so you need to adjust those darts as well. To start, draw a straight line through the horizontal bust dart to the apex. Cut along the line you just drew, as well as through one leg of the armhole dart, all the way to the marked apex.
Pivot the armhole dart legs closed. The bust dart will get larger, as you can see with the red paper above, but the armhole opening is now slightly smaller. If your garment has a sleeve, you usually can distribute the difference as ease to allow the sleeve to fit the armhole.
Does the shoulder slope cause drag lines? You'll need to make a muslin.
If your shape differs from the standard pattern's shoulder slope, then you might see some fit issues on the upper bodice and armhole. In this situation, a muslin test garment is a really good idea, and pin-fitting the pattern tissue on your body can work in a pinch — otherwise, you won't know of the issue until your garment is sewn up.
See the drag lines from the shoulder to the bust? That's a sign that the shoulders need more room. By releasing the shoulder seam, the bodice will relax and the lines will disappear. There are a number of ways you can adjust this.
For a square shoulder
On a square shoulder (where the top of the shoulder is more perpendicular to the neck, as opposed to sloping downwards), you need more room at the outer edge of the shoulder seam. If the neckline fits well, add to the pattern, as shown above with the orange paper.
For a sloping shoulder
If you have a sloping shoulder (the opposite of a square shoulder) then there will be too much room at the top of the armhole. In this case, pinch out the excess and adjust your pattern accordingly.
Using a muslin
A muslin test garment is really the best way to be sure of your adjustments. Make your muslin, but don't sew the shoulder seam closed. Enlist a fitting buddy, and have them pin the shoulder seam along the top of the shoulder, starting from just about under the ear and ending at the prominent bone on the outside of the shoulder. Mark this seam on both the front and back bodice pieces of your muslin.
You may have to add or take away different amounts on the front and back, which is perfectly fine and often necessary to get the shoulder seam in the right place.
Are the shoulders too wide or narrow? Edit your pattern piece.
The width of the shoulders can affect how the armholes fit. If there's a sleeve, then the seam should rest right at the edge of the shoulder and not hang over the arm (a sign of too much width). You have the opposite issue — needing more width — if the seam is pulling horizontally across the top of the bodice.
To widen the shoulders, add however much you need at the shoulder seam. Use a curved ruler and taper to zero around where the armhole notches are on front and back. Don't worry about precision here — if you add too much, you can remove a bit later.
To narrow the shoulders, do the same operation in reverse. I cut away the sections marked in orange from the pattern. Be careful not to take too much out of the pattern. Remember, you can always reduce further, but you can't add more fabric later one.
Is the armhole too low? Easily raise it to your liking.
Sleeveless dresses often have armholes that are too low for many people's taste. This also happens if you lengthen the bodice above the bust: The bottom of the armhole ends up in the wrong place (and your bra might show!).
On a garment with sleeves, a too low armhole reduces the mobility of the arm.
Here's another case where a test garment will really help. You can look in the mirror and measure one side to see how much to raise.
For a more exact measure, pin a piece of fabric inside the garment across the U-shape of the lower armhole. Then use a marking pen to draw in the exact spot where you want the armhole. Don't forget that you're marking the finished garment edge and that you'll need to add a seam allowance.
Interestingly, I've used vintage dress patterns from the '50s and '60s that included different bodices with a higher armhole for the sleeveless view. Even if you don't sew them up, vintage patterns can be a wealth of sewing and fit techniques!
One more note on all these armhole and shoulder seam adjustments...
You might need more than one!
For example, it's quite common to have a square shoulder slope as well as need more width. Some full-busted women might need both the reduction in armhole gaping and narrower shoulders.
I find it really helpful to make a test garment in the plain muslin cotton, and mark right on it with felt tip pens. Then you can really compare to your pattern tissue, see where the seams should be located and do your adjustments accordingly.