Getting the right fit in your upper arms can sometimes be tricky. Especially if you are more muscular or have chubbier upper arms, you will find that on some patterns the sleeves fit very snugly and the bicep seams are straining, resulting in an uncomfortable garment. Thankfully, there is an easy adjustment you can make for that, know as a Full Bicep Adjustment or Full Arm Adjustment.
With the Full Bicep Adjustment, you can add width to your sleeve. But, how will you know beforehand if a sleeve will be tight and more importantly how can you determine how much width you will need to add? Those are two good questions.
One way to check if a sleeve is going to be tight at the upper arms is of course to sew up a test garment (also know as toile/muslin) and evaluate the fit. However, there is an even easier method:
Using a tape measure, measure your upper arm at its widest part (the largest area between the elbow and the shoulder). The tape shouldn’t be too tight, nor too loose (you shouldn’t be able to fit a finger between the tape measure and your arm). Because our bodies aren’t always symmetrical, I recommend measuring both arms and going for the larger measurement. Yes, sometimes one arm tends to be larger that the other 🙂
Write down this measurement and then measure the widest part of the upper sleeve on your pattern piece. Don’t forget that you will have to subtract the seam allowance if it’s included in your pattern piece. In my example, I have drawn the seam allowance in red on my Sheona dress sleeve. The bicep line you are looking to measure is pretty much in line with the top edge of the pattern, where it hits the underam seam. That is the widest part of the upper sleeve.
Compare those two measurements to determine how much width you will need to add to your sleeve.
One important factor to keep in mind is the ease, which is the extra centimeters or inches built into a pattern for comfort and movement. If you are making a woven garment, you will need to add at least 4-5 cm (1,5-2″) of ease. If you are making a knit garment, that ease can be around 2-2,5 cm (1″). That also depends on personal preference (how loose-fitting you want the garment to be) and the type of garment you are making (for example, if you are making a jacket, you will need more ease than if you are making a fancy dress)
Now that you have your magic number for this adjustment, it’s time to trace your sleeve pattern piece. Don’t forget to transfer all the markings, such as the grainline and the notches.
Then, if your pattern includes seam allowance, measure it all around your pattern piece and draw the stitching line (marked with red in the photos below). Also, draw the hem allowance, if that’s included in your pattern piece.
Don’t get confused by the photo below, I drew my seam allowance on a sleeve copy I had already printed out of the PDF pattern and then decided to actually trace the entire piece on a white paper so you could see the lines more easily.
If you are adding up to a 2,5 cm (1″)
For this adjustment, we will be adding some extra room to the center of our sleeve. On your pattern piece, draw a horizontal line at the widest part of the upper sleeve (the bicep line I explained above, starting from one corner of the underarm seam to the other).
Next, draw a vertical line right at the center of your sleeve. To find that center, measure the bicep line you just drew, excluding the seam allowance, and divide it by two. This middle point is the center of your sleeve. The central line should go all the way from the sleeve head down to the hem and be parallel to the grainline.
Now, we are going to slash and spread out pattern piece. With a pair of scissors, cut along the two lines you just drew, being careful to stop a few milimetres before the stitching line. You will need to leave hinges, to be able to spread the pieces more easily. It’s helpful to start in the middle of your pattern piece and cut towards the edges.
Once you cut out along those lines, position an extra piece of paper underneath your pattern piece. Then, anchor down either the top or the bottom edge of your pattern piece and slowly spread apart the upperarm edges until the gap in the middle is as wide as the amount of ease you need to add to the sleeve. In my case, it was 2,5 cm (1″). Don’t worry that your top pattern pieces are going to overlap the bottom ones.
Check one more time that the middle gap measures correctly and then tape down those overlapping pieces, catching the extra paper underneath.
With this minor adjustment (addition of 2,5cm / 1 ” or less), the sleeve cap should not be affected. You may have to draw a new line on the top of the sleeve head, just to smooth it out a little and also smooth the hem line and sides. Then you can go ahead and use this new pattern piece or retrace it on a fresh piece of paper. It is always best to make a test garment first to check the fit of this adjusted piece, before you make your final garment.
If you are adding more than 2,5 cm (1″)
If you need to add more than 2,5cm (1″) of ease to your pattern piece, things are slightly different. This modification is slightly more complicated. Because the top pieces have to overlap much more, that affects the shape of the sleeve cap. As you will see in the photo below, the shape of the sleeve cap has changed, it is now more flat.
To amend this and make sure that the new sleeve will still fit into the armhole of your garment you will have to redraw the sleeve cap and then make the necessary changes to the front and back bodice of your garment. As this is a bit tricky to explain in photos, I will direct you to a fantastic video by Aneka of Made To Sew. She is an amazing teacher and I think her video example will be much easier to understand than a blog post.
I hope you found this tutorial useful! Here are some links to other posts on Full Bicep Adjustments that you may want to read: