When fitting your sewing patterns, don't forget about the sleeves! A sleeve that's too tight can be uncomfortable and a sleeve that's too loose can be unflattering. But a few simple adjustments to your sewing pattern can make sure your sleeves are perfectly comfortable.
Measuring for sleeves
First, take note of the pattern's measurements
Start with the sleeve circumference at the bicep (the fullest part of the arm so a sleeve). Many sewing partners indicate the bicep circumference on the pattern piece, as you can see above.
If the measurement isn't printed on the pattern, you can measure the circumference across the pattern piece directly, taking care to subtract the seam allowances.
Next, measure your own arm
Then measure your own arm circumference at the fullest part of the bicep, which is usually near the underarm.
For this measurement, it pays to have a sewing buddy — but if you don't, it's OK. Use a large paper clip or clothespin to hold a tape measure together and slide it up to the fullest part of your arm. Then look in the mirror and note the measurement.
Finally, compare the two measurements
Compare your arm measurement to the measurement on the paper pattern.
If you're using aa woven fabric, the pattern measurement needs to be 1" to 4" larger than your bicep circumference for comfort and ease of movement. A slim-fittting blouse might be on the small end of that range; a coat or jacket in a thick fabric needs more space to be worn over layers.
Decide whether you need to change the circumference of the sleeve and read on to learn how to make those adjustments. Be sure to do the alterations to the pattern before you cut out your fabric.
If your bicep measurement is substantially larger than the pattern, you need to do a full bicep adjustment . I suggest tracing the pattern piece and doing the adjustments on the traced copy just because it will involve cutting up your pattern piece.
Step 1: Draw grainlines
To start, draw the grainline in the center of the sleeve pattern piece, from the sleeve cap to the hem. Draw the line from one underarm to the other, perpendicular to the straight center grain line.
Step 2: Cut pattern along lines
Now cut through your pattern along the lines. It helps to keep a small hinge of paper at the outer edge of each cut to keep it intact when you start moving the pattern piece around. The hinge allows the paper to stay together at the edges.
Step 3: Add width across the arm circumference
To add more width in the sleeve at the upper arm, pull the sides of the pattern piece away from each other. With this approach, you're adding extra space to the center of the sleeve. On your body, that extra fabric will be on the outside of the arm.
The sleeve cap will drop down slightly, as shown with the green paper peeking out at the sleeve cap. Keep the bottom edge of the pattern level and let the pieces overlap at the crossways cut.
The benefit of doing this adjustment is that it does not substantially change the sleeve and consequently it will still fit into the armhole of your garment as designed. I like to retrace this outline onto one solid piece of paper. Be sure to transfer all notches and other sleeve markings.
Narrow bicep adjustment
If your bicep measurement is substantially smaller than the pattern, you might want to make the sleeve circumference smaller.
To do this, first follow Step 1 for a full bicep adjustment to cut the pattern piece.
Then, instead of spreading the pieces apart, you'll do the reverse. Move the sides to overlap at the center, taking out some of the fullness.
Like the full bicep adjustment, this change will not substantially change the sleeve cap, so you can insert your sleeve into your garment easily.
Adjust at the underarm
Another option to give a bit more room at the bicep is to add at the seam allowance as shown above. You can add up to ¾" on each seam allowance. Either ease the addition into the armhole or add a bit at the underarm on the front and back bodice.
If you're adjusting the side seams of your garment as well, then this is a quick way to adjust the sleeve for additional room to make it match your adjusted garment bodice.
Two-piece sleeve adjustment
Some sleeve patterns — particularly on coats and jackets — are constructed in two pieces.
In this case, you can to the seam allowance of seam on the back of the arm (the one shown above in the center of the sleeve). Make the addition right where the sleeve crosses over the fullest part of the arm and then gradually taper back to nothing at the sleeve cap and the hem. In the photo above, I also added a bit to the underarm seam, to achieve about 2" of increase in bicep circumference.
Don't forget to check the sleeve cap height — sometimes a sleeve may seem to narrow but actually the pulling caused when there is not enough length in the sleeve cap.