Three cast-on questions, one card: how many stitches your width needs (snapped to 1×1 or 2×2 ribbing), how long a tail the long-tail cast-on wants, and, for bands, the buttonhole placement along the band.
Your Cast On
Stitch pattern
Cast On
90stitches
for 18 in at 20 sts per 4 in
- Exact before snapping90.0 sts
- Width you’ll get18.00 in
- Long-tail to pull54 in + a hand’s length
The Formulas
stitches = width × stitches per inch, snapped to the pattern’s multiplelong-tail length ≈ 3 × the finished width, plus a hand’s length to holdThe tail rule is the old one and it holds: each stitch spends roughly an inch of tail at worsted gauge, which works out near three times the fabric width. Fine yarns spend a little less, bulky a little more, the hand’s length of grace absorbs both.
Worked Example
A hat brim in k2 p2 rib, in the round: 18 in around at 20 sts per 4 in (5 per inch):
- Raw: 18 × 5 = 90 → k2 p2 in the round wants a multiple of 4 → 88 stitches.
- Long tail: about 3 × 18 = 54 in plus a hand’s length: pull two arm-lengths and stop measuring.
- 88 at 5 per inch knits up 17.6 in: negative ease a hat is glad of.
Pattern Multiples That Matter at Cast-On
| Pattern | Flat | In the round |
|---|---|---|
| Stockinette, garter | any | any |
| K1 p1 rib | even (+1 for balance) | even |
| K2 p2 rib | 4 + 2 | multiple of 4 |
| Seed stitch | odd | even |
| 3 × 1 rib | 4 + 3 | multiple of 4 |
How to Choose Your Inputs
- Gauge in the pattern stitch: ribbing’s stitch gauge measured relaxed differs wildly from stretched: measure it the way it will be worn.
- Width: body measurement plus ease for garments; head circumference minus an inch or two for hats.
- Flat vs round changes the multiple, the chart above carries both for the common patterns.
Assumptions and Defaults
- Counts round to the nearest pattern-legal number, downward on ties for round work (snugger beats sloppier).
- Buttonhole spacing puts half-gaps at the two ends, the classic band layout: using the same even-spread math as the shaping calculators.
- The tail estimate suits long-tail and its cousins; backward-loop and cable cast-ons take whatever tail you like.
Cast-On Questions, Answered
How many stitches do I cast on?
The number of stitches to cast on is the width times your stitches per inch, rounded to fit the stitch pattern, so the 18 in k2p2 hat at 5 stitches per inch casts on 88. Your gauge comes from your own swatch, and that rounding step is why band patterns ask for counts like a multiple of 4 plus 2.
How long a tail do I need for a long-tail cast on?
A long-tail cast on needs a tail about three times the width you are casting on, plus a hand’s length, so a 20 in blanket edge needs roughly a 65 in tail. If you have ever run short three stitches from the end, the two-strand method, casting on from both ends of the ball, removes the guesswork entirely.
How do I space buttonholes evenly?
To space buttonholes evenly, leave half-gaps at the two ends and full gaps between the holes, so 7 holes in a 112-stitch band fall about every 16 stitches, starting at stitch 8. Tick the band option above and the calculator writes out that row for your own count.
Why cast on fewer stitches for ribbed brims?
You cast on fewer stitches for a ribbed brim because rib stretches, so a hat cast on at full head size slides down over the eyes. One to two inches of negative ease, which is the reduced count the calculator suggests for work in the round, keeps the ribbing snug and doing its job.
Gauge ranges: Craft Yarn Council standards.