Sock Size to Stitch Count Calculator
Turn a foot circumference and your gauge into a cast-on count that actually fits, negative ease included.
Cast-on count
Fit starts with ease, not just measurement
A sock pattern's stated size (small/medium/large, or a specific circumference) is really describing the knit fabric’s relaxed circumference, not the foot it's meant for. This calculator starts from your actual foot measurement, shrinks it by a standard negative-ease percentage, and only then converts that smaller number to stitches using your gauge.
The result is a cast-on count sized for the fabric to do its job — stretching to fit snugly rather than sagging around the ankle.
Frequently Asked Questions
Why does a sock need negative ease at all?
Knit fabric stretches, and a sock relies on that stretch to grip the foot without sagging or bagging out. If you cast on for the exact measured circumference of the foot, the relaxed fabric ends up looser than the foot once you're wearing and walking in it. Working the fabric a bit smaller than the foot — 10 to 15% is the standard range — lets the stretch do its job.
How do I measure my foot circumference accurately?
Wrap a soft tape measure around the ball of your foot — the widest part, just behind the toes — while standing with your weight on that foot, since feet spread slightly under load. Measure snugly but without compressing the tape into the skin.
Why round to a stitch multiple?
Many sock patterns use a repeating stitch pattern for the cuff or leg — a k2p2 rib needs a stitch count divisible by 4, for instance. Casting on a count that doesn't divide evenly into the repeat forces an awkward partial repeat at the round marker. Rounding the raw stitch count to the nearest multiple avoids that.
A craft planning aid, not foot-health or medical guidance. Always confirm fit against a real gauge swatch.