Sock Size Calculator
This knitting sock size calculator gives you a complete custom sock knitting pattern from your gauge and foot measurements: how many stitches to cast on for a sock (foot circumference × gauge with negative ease), a sock knitting size chart by shoe size, heel flap + row-by-row heel turn schedule, gusset pickup math, toe-up sock mode, sock leg length planner and a yarn estimate — for baby, child, women's and men's sizes, in inches or centimeters.
Your gauge & foot
How to measure: wrap a tape around the ball of the foot for circumference; stand on the tape, heel to longest toe, for length.
Cast-on calculator
Sock knitting size chart
Standard sock knitting foot length, foot circumference and leg length by size — look up your shoe size, or convert between US, UK and EU systems below. Values compiled from standard published sock sizing charts.
Shoe size converter
Heel math
Toe-up mode
Knit from the toe up: same final stitch count as cuff-down, but you start at the toe and try on as you go.
Cuff & leg planner
Your custom sock pattern
How the math works
Cast-on
cast-on = round₄(foot circumference × (1 − ease) × stitches per inch) — rounded to a multiple of 4 so 2×2 ribbing divides evenly and stitches split across 4 DPNs.
Heel flap
Worked over half the stitches. Flap length ≈ 28% of foot circumference (about 2–2¼″ for adults), converted to an even row count from your row gauge.
Heel turn
Simulated row by row using the standard published turn (k to 2 past center, ssk, k1, then sl1, work to 1 st before gap, decrease across the gap, k1/p1, turn). For a classic 32-stitch flap this produces 14 rows ending with 18 stitches — matching two independent published sock patterns; counts may vary ±1 stitch between pattern conventions.
Gusset
Pick up ≈ 1 stitch per 2 flap rows per side, rejoin the held instep stitches, then decrease 2 stitches every other round back to the cast-on count (a single extra decrease absorbs the odd stitch when the turn ends odd).
Toe
Wedge toe: decrease 4 stitches every other round to half the cast-on, then every round to a quarter (minimum 8), and graft. The foot is knit until foot length − toe length from the back of the heel.
Yarn
Calibrated so the reference adult-medium fingering sock (7½″ circumference) = 420 yards, scaling by foot area and the square of the gauge ratio. Treat as an estimate (±15%).
Scope boundary: this tool is sock-specific. For general knitting gauge math, garment sizing, needle/hook conversion and yarn substitution, see our knit & crochet lab.