Sock Size Calculator

How to use

1. Choose a preset foot size to fill in a typical circumference, or measure around the widest part of the foot — across the ball, just behind the toes — and enter that yourself.
2. Set the negative ease. Socks are knit smaller than the foot so they grip and stay up; 10% is a common starting point.
3. Enter your gauge: the stitch count and the width you measured it over. Sock yarn on 2.5mm needles is typically around 30 stitches per 10cm.
4. The pattern repeat is pre-filled with 4, because socks are almost always worked over a multiple of 4 for ribbing and for splitting evenly across needles. Change it if your stitch pattern needs something else.

Good to know

• Measure around the ball of the foot, not the ankle. That is the widest part the sock has to stretch over, and it is what the cast-on count needs to fit.
• Negative ease is what keeps a sock up. A sock knit at the exact foot measurement sags and slides down inside a shoe; one knit around 10% smaller hugs the foot. Use less ease for a non-stretchy fibre like cotton.
• Socks are conventionally worked over a multiple of 4 stitches — it divides evenly for K2 P2 ribbing and splits cleanly across double-pointed needles or a magic loop. 60 stitches for an adult medium in fingering weight is the classic result.
• The presets are typical reference circumferences, not measurements of any individual — foot width varies a lot at the same shoe size, so measure directly whenever you can.
• Always swatch in the round if you can. Many knitters get a different gauge working in the round than flat, and a sock is worked entirely in the round.

FAQ

How many stitches should I cast on for adult socks?

For fingering weight at around 30 stitches per 10cm, an adult medium usually lands at 60 stitches — but that is the output of a gauge and a foot measurement, not a rule. Enter your own numbers rather than trusting the common figure.

Where exactly do I measure my foot?

Around the ball of the foot — the widest part, just behind the toes. Keep the tape snug but not tight. That is the measurement the sock has to stretch over to go on.

How much negative ease do socks need?

Around 10% is a good default for wool or a wool blend. Too little and the sock sags in your shoe; too much and it is a fight to put on and wears out faster at the stress points.

Why is the pattern repeat pre-filled with 4?

Socks are worked in the round over a multiple of 4 almost universally — it splits evenly across needles and works with K2 P2 ribbing. You can change it if your stitch pattern has a different repeat.

Does this work for crochet socks?

Yes. Swatch in your crochet stitch, measure gauge the same way, and the count the calculator gives you is your starting round of working stitches.