Units

Calculator

Sock Cast-On Calculator

Tell us your foot circumference and your gauge — we'll give you the cuff cast-on count and the landmark stitch counts you'll hit at the heel and toe.

Calculator

Measure around the widest part of the foot — across the ball, not the arch, in inches. Adult medium is typically 8–9 inches.

Knit a swatch on small (US 0–3) needles with sock yarn, wash and block, then count the stitches across the standard 4 in swatch window — enter that count, not a per-in number. Sock fabric is dense — use smaller needles than the yarn label suggests.

Knitting and crochet gauge is measured over a standard swatch that is 4 inches — about 10 cm — square. Yarn labels and patterns use these two windows interchangeably, so "22 sts = 4 in" and "22 sts = 10 cm" mean the same thing. Enter your gauge however your pattern gives it and switch the unit toggle to match; your stitch count stays the same because it describes the same swatch. Finished measurements and yardage, where real lengths matter, are converted precisely (2.54 cm per inch).

Percent smaller than the foot. 10% is standard. Drop to 5% for very firm yarn; raise to 15% for very stretchy yarn or to keep socks up better.

Round to a multiple of N. Default 4 — fits k1p1 / k2p2 ribbing and most simple cables. Use 8 for wider repeats.

How this works

Knit Sock Anatomy Side-profile schematic of a cuff-down knit sock in the conventional L shape: a ribbed vertical leg tube at the top (cast on = 60 stitches), a distinct heel at the lower left built from a heel flap and a rounded heel turn worked over half the stitches (heel = 30), a gusset diagonal running from the front ankle back to the heel turn, a horizontal foot (instep on top, sole below), and a rounded toe at the right grafted closed over 16 stitches with Kitchener stitch. Stitch counts are derived from the sock-cast-on formula. Sock anatomy (cuff-down) Cuff & leg cast on = 60 Heel flap Heel turn heel = 30 Gusset Instep Sole Toe 16 (graft) Cast-on count drives the heel and toe stitch counts.
A top-down sock: cuff and leg, heel, foot, and toe.

Top-down socks cast on at the cuff and work down to the toe. The cast-on count needs to fit the leg snugly so the sock stays up — that's why socks use negative ease (a smaller stitch count than the foot circumference would suggest). The default 10% works for most yarns and feet. Drop to 5% for very firm yarn that won't stretch much, raise to 15% for very elastic yarn or feet that struggle to keep socks up.

Heel stitches are half the cast-on (the heel flap works on the back half of the sock). The toe-finish count is one-quarter of the cast-on, rounded to a multiple of 2 — that's the number you'll have when toe decreases finish and you're ready to graft the toe closed with Kitchener stitch.

Top-down only — for now

This calculator assumes top-down (cuff-down) construction. Toe-up socks start from a very small cast-on (typically Judy's Magic Cast-On, 16–24 stitches), then increase up to the foot circumference — that's a different math story that we'll add as a separate calc when demand warrants. If you knit toe-up, you can still use this calc to find your full foot-circumference stitch count, then plan your toe increases to reach that target.

Tips for measuring