Sock Cast-On Calculator
Take 10% off a 22 cm foot circumference and you are knitting to 19.8 cm, which is 59.4 stitches at 30 sts per 10 cm. Round that to 60, a multiple of four. Four matters twice over: a 2×2 rib repeats over four stitches, and the instep and sole have to split exactly in half (30 each) for the heel flap and gussets to come out symmetrical.
Your numbers
Cast-on stitches
60sts
Finished circumference
19.8cm
Formula
Cast-on stitches = 4 × round(Foot circumference × (1 − Negative ease ÷ 100) × Stitches per 10 cm ÷ 40)
Negative ease is not optional in socks. Knit to the measured circumference and the sock relaxes into folds under the foot and slides off the heel. Measure gauge in the round as well — the same yarn and needles give a different count worked flat.
What to enter
| Input | Default | Accepted range |
|---|---|---|
| Foot circumference (cm)The foot at its widest across the ball, taped over the instep. | 22 | 10 and up |
| Stitches per 10 cm (sts/10 cm)Stitches in 10 cm. If you measured over 5 cm, double it before entering. | 30 | 1 and up |
| Negative ease (%)How much smaller than the head you knit — what keeps a hat on. | 10 | 0 ~ 20 |
Step by step
Quick reference table
Results when only Foot circumference (cm) changes and everything else stays put.
| Foot circumference (cm) | Cast-on stitches (sts) | Finished circumference (cm) |
|---|---|---|
| 11 | 28 | 9.9 |
| 16.5 | 44 | 14.9 |
| 22 | 60 | 19.8 |
| 33 | 88 | 29.7 |
| 44 | 120 | 39.6 |
What each result means
| Result | At default values |
|---|---|
| Cast-on stitches (sts)Stitches to cast on; round to the pattern repeat. | 60 |
| Finished circumference (cm)The garment measured flat and unstretched, right round — not the body it fits. | 19.8 |
Common mistakes
Negative ease is not optional in socks. Knit to the measured circumference and the sock relaxes into folds under the foot and slides off the heel. Measure gauge in the round as well — the same yarn and needles give a different count worked flat.
Glossary
- Foot circumference
- The foot at its widest across the ball, taped over the instep.
- Stitches per 10 cm
- Stitches in 10 cm. If you measured over 5 cm, double it before entering.
- Negative ease
- How much smaller than the head you knit — what keeps a hat on.
- Cast-on stitches
- Stitches to cast on; round to the pattern repeat.
- Finished circumference
- The garment measured flat and unstretched, right round — not the body it fits.
Frequently asked questions
Q. How is Sock Cast-On Calculator calculated?
Cast-on stitches = 4 × round(Foot circumference × (1 − Negative ease ÷ 100) × Stitches per 10 cm ÷ 40) — Take 10% off a 22 cm foot circumference and you are knitting to 19.8 cm, which is 59.4 stitches at 30 sts per 10 cm. Round that to 60, a multiple of four. Four matters twice over: a 2×2 rib repeats over four stitches, and the instep and sole have to split exactly in half (30 each) for the heel flap and gussets to come out symmetrical.
Q. Can you walk through an example?
With Foot circumference 22cm, Stitches per 10 cm 30sts/10 cm, Negative ease 10%, the answer is Cast-on stitches 60sts.
Q. What do I need to enter?
Enter Foot circumference, Stitches per 10 cm, Negative ease. The result recalculates as you type, and an empty box counts as zero.
Q. How much does the answer move if I change a number?
Changing only Foot circumference (cm) moves the answer to Foot circumference (cm) 11 → Cast-on stitches (sts) 28 and Foot circumference (cm) 44 → Cast-on stitches (sts) 120. The table below lays out five steps.
Q. How are the numbers rounded?
Money is shown to the nearest whole unit, percentages to one decimal place and everything else to two. What you see is rounded; the calculation itself carries the unrounded value forward.
Q. Anything to watch out for?
Negative ease is not optional in socks. Knit to the measured circumference and the sock relaxes into folds under the foot and slides off the heel. Measure gauge in the round as well — the same yarn and needles give a different count worked flat.
Related calculators
Materials differ in density and absorption. If your label states a figure, use it — the defaults here are only common values.