Sock Knitting Calculator (Cast-On from Foot Size, Heel Flap, Toe Start & Yarn per Pair)

How it works

cast-on = foot circumference × (1 − negative ease) × sts/cm, rounded to a multiple of 4 · heel flap rows = heel stitches (half the cast-on); gusset pick-up = flap rows ÷ 2 + 1 per side · toe length ≈ 0.22 × sock circumference; start toe at foot length − toe length · yarn ≈ stitches × 3.1 × stitch width × 1.08 per sock

Socks fit because they are knitted smaller than the foot and stretch: about 10% negative ease around, and heel and toe shaping that take a predictable share of the foot length. From your gauge the calculator derives the cast-on, the classic square heel flap (as many rows as it has stitches), the gusset arithmetic, and the point on the foot where the toe decreases must begin so the finished length matches — the number most sock knitters get wrong. Yarn is estimated from stitch count and gauge, which is why a big foot in fingering weight can outrun a 100 g skein.

Worked example

A 23 cm foot and 25 cm length at 32 sts and 44 rounds per 10 cm: 10% negative ease gives a 20.7 cm target, so cast on 68 (21.3 cm). Cuff 11 rounds, leg 55; a 34-stitch heel flap of 34 rows, 12 stitches after the turn, 18 gusset stitches picked up each side (82 → 68 over 7 decrease rounds); knit the foot to 20.3 cm and start the toe with 13 decrease rounds. A pair takes about 260 m — roughly 65 g of a 400 m/100 g sock yarn.

Frequently asked questions