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Elizabeth Zimmermann started her business in the 1950s to supply hand-knitters with pure wool and circular needles — both hard to come by then — and is known for technique innovations of her own, the I-cord among them. Her percentage system answers a question most knitters reach eventually: how do I make a sweater that fits me, without following someone else’s instructions row by row?
EPS: Elizabeth's Percentage System
The core of Zimmermann's methodology is EPS (Elizabeth's Percentage System). The system starts from a single measurement — the chest circumference — turns it into a stitch count, and gives every other part of the sweater as a percentage of that number.
The Golden Formula (Proportions)
- Chest Circumference (Body Key Number / K): 100% (total body stitches)
- Sleeve at Wrist: approx. 20% of K (increasing gradually to 33%)
- Sleeve at Underarm: approx. 33% of K
- Underarm Cast-off / Steek: approx. 8% of K
- Yoke Depth: approx. 25% of the chest circumference
This system allows you to knit a sweater with any yarn and on any needle size, without having to follow a single specific pattern. It offers immense freedom when designing with handspun yarn, vintage skeins, or stash combinations.
How we knit it: in the round
We knit an EPS sweater in the round: body and sleeves as tubes, joined for the yoke, so the percentages give us stitch counts rather than pieces to sew together. Her EPS sweater pattern, linked below, is where the percentages come from.
A worked example
Say your swatch gives 5 stitches per inch and you want a sweater 40 in102 cm around. Working in inches, the key number K is 40 × 5 = 200 stitches. Then, with the percentages above:
- Sleeve at the wrist (20%): 40 stitches
- Sleeve at the underarm (33%): 66 stitches
- Underarm stitches set aside (8%): 16 stitches
- Yoke depth (25% of the circumference): 10 in25 cm
Round to whatever your stitch pattern needs — ribbing, a colorwork repeat. The percentages are approximate by design.
Why Learn Elizabeth Zimmermann's Percentage System?
While modern online tools (including our calculators) can automate the math, understanding the underlying proportional logic makes you a far more adaptable knitter:
- Custom Fit: You design precisely for your own body rather than standard industry sizing.
- Design Freedom: You can integrate stitch patterns, cables, or colorwork yokes seamlessly into the framework.
- No side seams: we knit body and sleeves in the round, so there are no side or sleeve seams to sew.
Tips to Get Started
Start with a chest measurement plus your desired ease. Use our gauge calculator to convert that circumference into your key stitch count (100%). From there, the EPS formulas give you the stitch numbers for every section of the sweater!
The percentages are Elizabeth Zimmermann’s own, as given in her EPS pattern. Her books are still published by her family’s own press, Schoolhouse Press, whose own history of the business is the source for what she is described as having done.