Sleeve Cap Ease Calculator
Whether a sleeve will ease into its armhole.
Calculate sleeve cap ease as a length and a percentage of the armhole, and whether it is within the range that will ease in without puckering.
Cap ease
1.20"
6.0% of the armhole
Within the usual range for a woven set-in sleeve. Measure along the seam lines rather than the cut edges — including seam allowance gives an ease figure that is wrong in both directions. To reduce ease, lower the cap height rather than narrowing the sleeve, which would make it tight at the bicep.
How the Sleeve Cap Ease Calculator works
A set-in sleeve cap is deliberately longer than the armhole it goes into, and the surplus is eased in to give room over the shoulder. Too little and the sleeve pulls; too much and it will not ease without puckering. The workable range is narrow — roughly three to ten percent of the armhole — and it is worth checking before the sleeve is cut.
Also known as: sleeve ease calculator · sleeve cap fitting calculator
A narrow workable range
A set-in sleeve cap is longer than the armhole it goes into, deliberately. The surplus is eased in around the top of the cap to create room for the shoulder to move forward, and without it the sleeve pulls across the back.
The workable range is narrow. One to one and a half inches on a typical armhole is five to eight percent, and that is what most woven patterns are drafted with. Below about three percent the sleeve is flat and restrictive; above ten it will not distribute smoothly and puckers.
Knits and shirt sleeves use much less because the fabric or the flatter cap does the work instead — a dropped-shoulder or shirt-style sleeve may have almost none.
A worked example
A 20 inch armhole with a 21.2 inch cap has 1.2 inches of ease, which is 6 percent — comfortably within range for a woven set-in sleeve.
Raise the cap so it measures 23 inches and the ease is 15 percent. That will not ease in on cotton poplin at all; on a soft wool it might, because wool shrinks and moulds under an iron in a way cotton does not. The fabric decides what is achievable as much as the number does.
Where the answer misleads
Both measurements must be taken along the seam lines, not the cut edges. Measuring the cut edge includes the seam allowance on curves of different radii, which produces an ease figure that is wrong in both directions and usually flatters the pattern.
The fix for too much ease is to lower the cap height, which shortens the curve without narrowing the sleeve. Taking width out instead makes the sleeve tight at the bicep, solving a problem you did not have.
Finally, ease is distributed unevenly around the cap: most of it goes into the top third, and almost none between the notches at the underarm. A cap with the right total ease distributed evenly will still not set in cleanly.
Frequently asked questions
How much ease should a sleeve cap have?
One to one and a half inches for a woven set-in sleeve, which on a typical armhole is five to eight percent. Shirt sleeves and knits use much less, often under three percent.
My sleeve cap is too big. What do I do?
Reduce the cap height slightly, which shortens the curve without narrowing the sleeve. Taking width out instead makes the sleeve tight at the bicep, which is rarely the problem you were trying to solve.
Why does my sleeve pucker?
Usually too much ease for the fabric. Wool eases beautifully, cotton poplin does not, and a cap drafted for one will pucker in the other. Above about ten percent, most wovens will not distribute the surplus smoothly.
How do I measure the cap and armhole?
Stand a tape on its edge and walk it along each seam line, not the cut edge, from underarm to underarm. Measuring the cut edge includes the seam allowance and gives an ease figure that is wrong in both directions.