Sock Sizing Calculator

This calculator works out cast-on stitches and the row counts for the major structural sections of a traditional heel-flap sock — leg, heel flap, gusset, and toe — from just your foot measurements and stitch gauge. Like the hat calculator, it applies 10% negative ease to your foot circumference before converting to stitches, since socks need to stretch snugly around the foot rather than hang loose; the resulting stitch count is then rounded to the nearest multiple of 4 so it divides evenly across a typical 4-needle DPN or two-circular setup. The heel flap is treated as a square: its stitch width (half the total cast-on) is also used as its row count, which is the standard rule of thumb for turning a heel that sits flush against the leg. Gusset pickup stitches are estimated as half the heel flap row count, matching the common slipped-stitch selvage convention where every other row forms a chain-like edge loop along the flap, so you pick up roughly one stitch per two rows rather than one per row.

Foot length in rounds is derived by subtracting an allowance of 40% of your foot circumference from your total foot length before converting to stitches — that allowance approximates the combined length taken up by the heel turn and toe shaping, so what's left is the plain foot tube. Toe decreases are estimated at one-eighth of the cast-on count. As with any gauge-driven calculator, the numbers are only as good as your swatch: sock yarn commonly knits at 7-9 stitches per inch, and a mismatch between swatch and in-the-round tension will shift every downstream count.