Tutorial - How to widen a sleeve at the biceps

Here is how to widen a sleeve at the biceps WITHOUT altering the armhole of your pattern.

1-measure your arm circumference at the widest point = biceps

2-add 1 cm for ease

3-measure Y the width of the pattern piece at the biceps level (a few centimeters below the armhole)

4-calculate your adjustment = arm circumference + 1 cm ease - Y + seam allowances (because they are included in ikatee patterns)
for example:
Y = 32 cm including seam allowances
arm circumference = 33cm
arm circumference + ease = 34cm
seam allowances on each side: 2*1cm = 2cm
adjustment to make = 34-32+2 = 4cm

5-Place the sleeve piece on a sheet of paper and draw a line parallel to the sleeve sides at X cm (X = adjustment / 2 because the adjustment is split on each side. In the example X = 4/2 = 2cm

6-Pin a pin at the top of the sleeve head and rotate the sleeve piece around the pin until the bottom of the armhole touches the widening line drawn in red… redraw on your paper the front armhole curve along the pattern piece (in green on the drawing). Then repeat the operation on the back of the sleeve.

7-Redraw the pattern piece (in green): the armhole is moved but keeps the same shape on the front and back; the sleeve is widened at the biceps. It is possible to reduce the sleeve hem afterwards (which will barely affect the biceps widening)

And in video: