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Sock size calculator for knitting: cast on, heel and toe

Enter foot measurements or a shoe size and your gauge to get the cast-on, heel flap, gusset, foot length and toe for hand-knit socks.

Foot size from

Foot length

Foot circumference

Leg length, cuff to heel

Unit

Stitches

Rounds

Measured over

Negative ease (%)

Stitch count multiple

Shoe size to foot length (approximate)

Foot length	US women’s	US men’s	UK	EU
8.5 in 21.6 cm	4.5	3.5	2.5	35
8.75 in 22.2 cm	5.5	4.5	3.5	36
9 in 22.9 cm	6	5	4	37
9.25 in 23.5 cm	7	6	5	37
9.5 in 24.1 cm	7.5	6.5	5.5	38
9.75 in 24.8 cm	8.5	7.5	6.5	39
10 in 25.4 cm	9	8	7	40
10.25 in 26 cm	10	9	8	41
10.5 in 26.7 cm	10.5	9.5	8.5	42
10.75 in 27.3 cm	11.5	10.5	9.5	43
11 in 27.9 cm	12	11	10	44
11.25 in 28.6 cm	13	12	11	45
11.5 in 29.2 cm	13.5	12.5	11.5	46
11.75 in 29.8 cm	14.5	13.5	12.5	47

Shoe sizes are rounded to the nearest half size and vary between brands. Use the table for gifts; measure the foot when you can.

Measuring a foot for socks

Measure standing up, because feet spread under weight. For length, stand on a sheet of paper with the heel against a wall and mark the tip of the longest toe. For circumference, wrap a soft tape around the ball of the foot, the widest part just behind the toes, snug but not tight.

How the sock is calculated

The cast-on is the foot circumference minus the negative ease, multiplied by your stitch gauge and rounded to your rib multiple. The heel flap uses half the stitches and is worked for the same number of rows, a slip-stitch heel flap that comes out about square. You then pick up one stitch for every two flap rows, plus one, along each side for the gusset.

For the foot, the calculator works out how long your toe will be from the number of decrease rounds and your row gauge, then subtracts it from the foot length, minus a further 2% so the finished sock is not baggy at the toe.

Sock yarn is usually super fine (1) weight. Check its needle range in the needle size converter, or identify an unlabelled yarn with the WPI calculator.

How to use it

Measure the foot: length from the back of the heel to the tip of the longest toe, and circumference around the widest part of the ball of the foot. No tape measure? Use a shoe size for an estimate.
Enter your gauge in stockinette in the round, measured on a washed swatch.
Choose the negative ease (10% is a snug, standard fit) and the stitch multiple your cuff pattern needs.
Follow the numbers for the cast-on, leg, heel flap, gusset, foot and toe. Toe-up knitters can use the same numbers in reverse.

Questions

How many stitches do I cast on for socks?

Multiply your foot circumference by your stitches per inch, then take off about 10% for a snug fit. With fingering yarn at 32 stitches per 4 inches (8 per inch) and an 8½ inch foot, that is 8.5 × 8 × 0.9 ≈ 61, rounded to 60 or 64.

How much negative ease do socks need?

Most hand-knit socks are made 10% smaller around than the foot so they cling without sagging. Use 5% for a looser fit or a non-stretchy stitch pattern, and up to 15% for very stretchy ribbing.

When do I start the toe?

Start the toe when the foot measures the total foot length minus the length of the toe, plus a little extra snugness. The calculator works out the toe length from your stitch count and row gauge and gives the exact measurement.

How long should the leg of a sock be?

A crew sock leg is usually 6–7 inches from cuff to heel, an ankle sock 2–3 inches and a knee sock 12 inches or more. Leg length does not depend on foot size, so choose what you like to wear.

Can I use shoe size instead of measuring?

You can for an estimate. The calculator converts shoe size to an approximate foot length and assumes the circumference is about 95% of the length, as Knitty’s foot survey found on average. Feet vary a lot within one shoe size, so measure if you can.