How to use the sock calculator
- Measure around the ball of the foot and from the back of the heel to the end of the longest toe.
- Knit a swatch in the round in stockinette, wash it, and count stitches and rows over 4 inches or 10 cm.
- Leave negative ease at 10 percent or adjust it.
- Pick 2x2 or 1x1 rib for the cuff. That sets whether the cast-on rounds to a multiple of 4 or 2.
- Follow the plan from the top: cuff and leg, heel flap, heel turn, gusset, foot, toe, graft.
How a heel flap sock fits together
The leg is a tube of the cast-on count. At the heel, half the stitches are worked back and forth into a flap that covers the back of the heel, while the other half wait for the instep. Short rows then turn the heel, cupping the bottom of it.
To go back to working in the round you pick up stitches along both edges of the flap. That gives more stitches than the cast-on, and the extra make the gusset, a triangle of fabric on each side of the foot that fits over the instep. Decreases at the sole bring the count back down. The foot is then knitted straight until it is time for the toe, which narrows on both sides like a wedge and is grafted closed.
Formulas
- Cast on = foot circumference × (1 − ease %) × stitches per inch, rounded to a multiple of 4 or 2.
- Heel flap stitches = cast on ÷ 2; heel flap rows = heel flap stitches.
- Gusset pick-up per side = heel flap rows ÷ 2.
- Gusset decrease rounds = (instep + heel turn + 2 × pick-up − cast on) ÷ 2.
- Toe decrease rounds ≈ cast on × 0.75 ÷ 4, so about a quarter of the stitches remain.
- Foot before toe = foot length − toe rounds ÷ rows per inch.
- Kitchener stitch = stitches left ÷ 2 on each needle.
Worked example: an 8 inch foot
At 32 stitches per 4 inches you get 8 per inch. The foot measures 8 inches around, and 10 percent smaller is 7.2 inches, so 7.2 × 8 = 57.6 stitches. The nearest multiple of 4 is 56, which makes a 7 inch sock, 12.5 percent smaller than the foot.
The heel flap is 28 stitches for 28 rows. The turn starts with sl 1, k15, ssk, k1 and leaves 16 stitches. Pick up 14 along each side: 28 instep + 16 heel + 28 picked up = 72. To get back to 56, work 8 decrease rounds.
The toe decreases 4 stitches every other round 7 times, down to 28, then every round 4 times, leaving 12. That is 18 rounds, and at 11 rows per inch about 1.64 inches. For a 9.5 inch foot, start the toe at 7.86 inches and graft 6 stitches from each needle.
Cast-on stitches by foot size
With 10 percent negative ease and a multiple of 4.
| Foot around | 28 sts per 4 in | 32 sts per 4 in | 36 sts per 4 in |
|---|---|---|---|
| 7 in | 44 | 52 | 56 |
| 7.5 in | 48 | 56 | 60 |
| 8 in | 52 | 56 | 64 |
| 8.5 in | 52 | 60 | 68 |
| 9 in | 56 | 64 | 72 |
| 9.5 in | 60 | 68 | 76 |
| 10 in | 64 | 72 | 80 |
Heel, gusset and toe counts by cast-on
Every count after the cast-on follows from it. These rows use 32 stitches and 44 rounds per 4 inches.
| Cast on | Heel flap | Pick up each side | Gusset decrease rounds | Toe rounds | Graft |
|---|---|---|---|---|---|
| 48 | 24 sts, 24 rows | 12 | 7 | 15 (1.36 in) | 12 |
| 56 | 28 sts, 28 rows | 14 | 8 | 18 (1.64 in) | 12 |
| 60 | 30 sts, 30 rows | 15 | 9 | 18 (1.64 in) | 16 |
| 64 | 32 sts, 32 rows | 16 | 9 | 20 (1.82 in) | 16 |
| 68 | 34 sts, 34 rows | 17 | 10 | 21 (1.91 in) | 16 |
| 72 | 36 sts, 36 rows | 18 | 10 | 23 (2.09 in) | 16 |
How ease and rounding change the cast-on
For the 8 inch foot at 8 stitches per inch, the ease setting and the rib multiple both move the count. A multiple of 4 jumps in steps of half an inch at this gauge, so two settings can land on the same number.
| Ease setting | Cast on | Sock around | Actual ease |
|---|---|---|---|
| 0% | 64 | 8 in | 0% |
| 5% | 60 | 7.5 in | 6.3% |
| 10% | 56 | 7 in | 12.5% |
| 15% | 56 | 7 in | 12.5% |
| 20% | 52 | 6.5 in | 18.8% |
Other formulas round differently. GoodKnit Kisses also takes off 10 percent but rounds to the nearest even number, which turns the same 57.6 stitches into 58. That suits 1x1 rib; for 2x2 rib you need a multiple of 4, which is why this calculator gives 56. Katia rounds down in its examples and does not take off ease at all. If your result sits close to halfway, try both options and look at the actual ease column in the results.
Compared with a published sock chart
The Needle & Arts basic sock formula lists adult cast-ons by yarn weight. It notes that socks are usually knitted at a tighter tension than normal because they stretch with wear.
| Size | Sock yarn (30 to 32 sts) | DK (24 to 26 sts) | Worsted (20 to 22 sts) |
|---|---|---|---|
| Small adult | 60 | 48 | 40 |
| Medium adult | 60 | 48 | 40 |
| Large adult | 64 | 52 | 44 |
| X-large adult | 68 | 56 | 48 |
Gauges are per 4 inches. The chart gives no foot sizes, so use it as a cross-check. An 8 inch foot at 32 stitches per 4 inches comes out at 56 here, a little under the chart's small adult 60. The same formula works its heel flap for 2 rows fewer than the flap has stitches, and picks up one extra stitch in each corner of the gusset. This calculator uses as many rows as stitches, following the Dummies pattern, so its flap is 2 rows longer. The pick-up comes out the same: for a 28 stitch flap, Needle & Arts picks up 13 edge stitches plus 1 corner stitch, and the calculator picks up 14. To measure the foot itself, see how to measure feet for socks.
Tips for sock knitting
- Slip the first stitch of every heel flap row. The slipped edge gives you neat loops to pick up.
- Pick up one extra stitch in the corner between flap and instep if a hole tends to form there, then decrease it on the next round.
- Try the sock on before starting the toe. Stretch it lightly along the foot as you would wear it.
- Write down every count for the first sock. Matching the second one is much easier.
- Swatch in the round if you will knit the sock in the round. Gauge can differ between flat and circular knitting.