Sleeve Cap Adjustments Due to Height

Height adjustments are made at the lines indicated

Getting the armhole right is one of the most difficult parts of pattern making and modifying existing patterns.

The best way to measure your armhole depth is to take something flexible like a magazine or a thick pad of paper. Hold it under your arm parallel to the floor and bend it around to the front  of your body. Measure from the top of your shoulder down to the straight edge of the item tucked under your arm. Measure at the outside edge since the sleeve cap attaches there. If you are modifying an existing pattern remember that on a sloped shoulder the measurement is longer on the inside edge of the shoulder. Normally the schematic will reflect this. Add 1 - 2 inches to your personal measurement for ease.

The lines on the schematic pictured above show where you would add or remove length to adjust your garment for better fit.
 
A sleeve cap should fit easily into the armhole without having to be stretched or squeezed to fit. In knitted garments the sleeve cap is symmetrical, however if you are having major fit problems in this area you can consider making the cap fuller on the backside edge by slowing the rate of decrease. Look at the back of most women’s arms and you will see that often it’s much fuller than the front.  

Cap height is shorter than the total armhole depth. It is based roughly on a proportion to bust measurement. For busts up to 30 inches the sleeve cap is 2 inches less than armhole depth for 30 – 48 inch busts it is 3 inches less and over 48 inches it is 4 inches less. 

This info is meant as a starting point only, as cap height can be manipulated for better fit in a number of ways. As an example, when narrowing a sleeve for a closer fit, the cap must become higher to reach the same final cap length to fit into the armhole.

The length of the armhole and the sleeve cap are closely related

 
The beginning of the sleeve cap starts with cast offs and decreases that match those of the underarm. The next section tapers the sides until you are about 1 inch away from the top edge. The third section casts off stitches quickly at the amount of 1 inch or less worth at each end and the last cast offs should be in the amount of stitches equal to .25 of the upper arm width. The last 2 cast off segments vary in width according to designer, generally the very flat topped sleeve caps create a loose fit. You can use graph paper and plot in the numbers you know and then draw in the rest. Your cap should be a little bigger than the armhole by approximately 1 - 1.5 inches and should be set in smoothly across the top of the shoulder with a little easing on the sides. To measure, chart both the armhole and the sleeve cap on knitters graph paper. You can then use a flexible ruler or a tape measure standing on its side to compare the two. It is surprisingly difficult to do this on a first try. I usually have to fiddle around with the decreasing and shaping to work out the sections between the initial cast offs that match the underarm and the top of the cap which I drawn in according to row count. 

You should know also that designers vary widely on how they create sleeve caps. They also differ on opinions as to the fit of the cap. I like a larger cap eased into the armhole. Some prefer an exact match and still others prefer to stretch the cap to fit.