If your garments often feel tight around the upper arms, a full biceps adjustment could make them more comfortable for you. And this time, in order to figure out how much width to add to your sleeves, you don’t have to sew a muslin! You can simply compare your biceps measurement to the pattern piece (but don’t forget to add at least 5 cm/2″ of ease). For instance, for a size 40 sleeve and a 30 cm biceps measurement:
30 cm (biceps measurement)
– 34 cm (pattern piece width)
+ 5 cm (ease)
+ 2 cm (seam allowances)
= 3 cm to add to the sleeve width
This modification is particularly easy on short sleeves like the Sirocco‘s: we’ll simply add the same width below the armhole down to the hem.
1/ Draw a vertical line parallel to the straight grain and going through the dot that indicates the top of the sleeve. Draw a second line, perpendicular to the first, 1.5 cm (5/8″) below the armhole.
2/ Slash along the vertical line, leaving a pivot point at the dot, and pivot both parts of the sleeve to reach the desired width (measure at the level of the horizontal lines).
3/ Slash along the horizontal lines, leaving pivot points at the side seams. Pivot the lower parts of the sleeve so that their edges are parallel to the straight grain again.
4/ Take a new sheet of pattern paper and trace the edges of the sleeve. Draw a new horizontal hemline, perpendicular to the straight grain.
Here’s your new sleeve! Note that the sleeve head length hasn’t changed, so you won’t have to ease in anything to assemble it to the bodice.