Sleeves that fit well add to the comfort and wearability of any garment. With these few steps you can alter your sleeve pattern pieces and create a shirt, jacket or dress with sleeves that are just right instead of too tight!
Even if the bodice of a garment fits well, sometimes once the sleeves are sewn on it feels restrictive and limits arm movement. One frequent cause of this is a sleeve that is too tight in the bicep. The "bicep adjustment" is one sleeve alteration that needs to be done on your pattern piece, so you can cut out a sleeve that will fit the body.
Here are the steps to doing a bicep adjustment for a sleeve that fits like a dream!
Step 1: Measure your arm at the bicep and compare to the pattern.
Some patterns have the finished bicep circumference measurement printed on the pattern but if isn't that's no problem. Measure from seam allowance to seam allowance horizontally at the underarm, note that number and compare to your own bicep circumference.
To measure your arm it's best to have a helper - keep your arm relaxed and measure around the bicep just at the underarm. For a woven fabric 1.5 to 2 inches of ease is comfortable, although you can go down to about 1 inch if sewing a knit. For a winter coat or jacket you may need even more sleeve ease as you might be wearing the item over a sweater.
Perfectly fit knits will soon be yours!
2. Trace the original sleeve cap.
Draw two lines on your sleeve pattern, Line A shown above horizontally from seam allowance to seam allowance, just at the underarm. Line B is vertical, at a right angle to the first, from the center of the top of the sleeve cap to the bottom edge of the sleeve. Then pin your sleeve on some paper, and trace a line around the entire sleeve cap as shown.
Step 3: Spread the sleeve to add width at the bicep.
To adjust the sleeve width at the bicep, slice through the vertical and horizontal lines created in the previous step, just up to the seam allowance. You will spread the pattern at the center the amount required to create more width at the bicep. It helps to make small cuts in the seam allowance, leaving a small hinge of paper so you can spread the pattern piece but it will still be attached to the sleeve cap portion.
Note: When you spread the pattern apart the sleeve cap is pulled down but since we traced the outline of the original sleeve cap in Step 2 that will remain and the sleeve will still match the original armhole on the pattern. Tape it in place and cut out or trace your new sleeve pattern. Be sure to measure the new sleeve circumference at the horizontal line to make sure you have added the required amount based on your measurements determined in Step 1.
Step 4: Adjust the bodice front and back.
Also note that in Step 3 above when we spread the sleeve apart at the center to make more room, the sleeve cap seam line has also increased a bit on each side. If it totals more than an inch it can be difficult to ease that into the armhole, so you will need to add that amount to the front and back bodice. You can add at the underarm and gradually taper to nothing at the waist or above.
Instead of adding to the side seams to accommodate the addition to the sleeve cap seam line another option is to deepen the armhole slightly at the underarm. This serves to make the actual armhole seam line a bit longer, matching the new sleeve cap seam line and allows you to ease in the now larger sleeve.
One last item to note - once you have added width to the bicep area of a sleeve - take a look at the sleeve width at the lower part of the arm. You will probably want to taper that sleeve seam in back to the original width on the pattern piece.
So give this a try and you will have a garment with nicely fitting sleeves — no sweater required when someone turns up the air conditioning.