How tall should a sleeve cap be?

A standard set-in sleeve cap is approximately 60-70% of the armhole depth. For a 20cm armhole, the cap would be 12-14cm tall. A taller cap gives a fitted look; a shallower cap gives more ease of movement.

How do I shape a sleeve cap?

Bind off the same number of stitches as the body armhole at each side (the underarm bind-off). Then decrease 1 stitch each side in two phases — gently every other (RS) row up the lower cap, then more steeply every row approaching the top — so the decreases form a bell curve over the full cap height. Finally, bind off the remaining stitches straight across the top. The flat top should measure roughly a quarter of the upper arm width (upper arm ÷ 4 − 0.5cm), not a wide square shoulder.

Why does my sleeve cap not fit the armhole?

The cap perimeter must match the armhole perimeter. If the cap is too big, decrease more aggressively. If too small, decrease more slowly. A small amount of ease (1-2cm extra) is normal.

What is the difference between set-in and raglan sleeves?

Set-in sleeves have a shaped cap that fits into a curved armhole, giving a tailored look. Raglan sleeves use diagonal decrease lines from underarm to neck. Set-in sleeves require more shaping but give a classic, fitted shoulder.

How do I ease a sleeve cap into the armhole?

Pin the cap into the armhole at shoulder, underarm, and midpoints. Ease any extra fullness evenly. A small amount of ease creates the rounded shoulder shape. Steam blocking helps settle the ease.

KnitCalcs

Set-In Sleeve Calculator — Sleeve Cap Shaping

Calculate sleeve cap shaping for set-in sleeve construction based on armhole depth and upper arm measurements.

Armhole Depth

Depth of the body armhole

Upper Arm Circumference

Widest part of upper arm

Stitch Gauge (per 10cm)

Stitches per 10cm from your gauge swatch

Row Gauge (per 10cm)

Rows per 10cm from your gauge swatch

How We Calculate This

This calculator determines sleeve cap shaping based on standard proportions.

The formula

Cap height = Armhole depth x 0.65

Cap stitches = Upper arm circumference x stitch gauge

Base bind-off = ~8% of cap stitches each side (matches the body armhole bind-off)

Top bind-off = Upper arm ÷ 4 − 0.5cm (≈ a quarter of the upper arm width)

The remaining stitches are decreased 1 each side in two phases — every 2nd row low on the cap, then every row near the top — so the shaping fills the whole cap height in a bell curve.

Frequently Asked Questions

Related Calculators

Raglan Calculator

Calculate raglan decrease rates and yoke depth for top-down or bottom-up construction.

Neckline Calculator

Calculate neckline shaping for round, V-neck, and boat neck styles.

Armhole Calculator

Calculate armhole depth and bind-off shaping for fitted garments.

Shoulder Shaping Calculator

Calculate short-row or bind-off shoulder shaping steps.

Short Row Calculator

Calculate short row wraps and turns for bust darts and curved hems.

Last updated: February 2026

All calculations are estimates based on standard yarn weights and gauge. Results may vary with individual tension, yarn brand, and needle size.