Sock size calculator

Sock stitch counts come from the ball of the foot, not from a shoe size, and they need negative ease so the sock stays up and does not wrinkle under the heel. The Craft Yarn Council publishes foot circumferences and sock heights for babies through adults, which is what this calculator reads your measurement against — but the ease itself is your decision, because the standard does not publish one. Ten per cent is the usual starting point and the default here.

How it is worked out

cast on = foot circumference × (1 − ease) × gauge, rounded to your repeat

A sock is a tube worked at a tighter gauge than most knitting — sock yarn on 2.25 to 2.75 mm needles — so small errors compound quickly around a small circumference. Rounding to four is the usual choice because it divides evenly over four double-pointed needles as well as over a 2×2 rib.

Source: circumference × density, less the ease chosen by the knitter

The published foot chart

Every row as the Craft Yarn Council prints it, in both units. One sock height carries a dash: for the Woman 4–6½ band the standard gives 6½ inches and 6.5 cm, which cannot both be true, so we keep the inches and leave the other cell empty rather than convert it ourselves.

Questions people ask

Where exactly do I measure?

Around the widest part of the foot, across the ball, with the tape snug but not pulling. That is the measurement the published chart lists, and it is the one the sock has to stretch over — the ankle is usually narrower, which is why a sock knitted to the ankle slides down.

Why is one sock height missing from the chart below?

Because the standard contradicts itself on that row. The Woman 4–6½ band gives a sock height of 6½ inches and 6.5 cm, and those are not the same length — 6½ inches is 16.5 cm, and 6.5 cm is the figure from the baby row further up the same page. Rather than pick one and present it as published, or silently convert the inches ourselves, we keep the inch figure and leave the centimetre cell empty.

How much ease do socks need?

Around ten per cent, so a 23 cm foot gets a sock of roughly 20.5 cm. Sock fabric worked at a tight gauge has less give than it looks, and a sock knitted to the exact foot measurement will feel loose after an hour of wear. This is convention rather than standard: the Craft Yarn Council publishes the foot, not the fit.

Does this cover the heel and the toe?

No — it gives the cast-on for the leg and the foot, which is the number everything else follows from. Heel construction differs so much between methods that a single formula would be wrong for most of them: a heel flap takes half the stitches, a short-row heel takes a different half, and an afterthought heel takes none until later.

Can I use this for crochet socks?

Yes, with one warning: crochet fabric stretches less than knitted fabric of the same gauge, so start nearer five per cent of ease than ten and check the tube over your own foot before working the heel.

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