How it works
Plain stitches = stitches now − 2 × decreases
Gaps = decreases + 1 (flat) or decreases (in the round)
Each gap = plain ÷ gaps; the remainder gets 1 extra stitch per gap
Each decrease works two stitches together and turns them into one. So if you start with S stitches and want to lose D, the decreases themselves use 2 x D stitches, and the rest, S - 2D, are plain stitches you share out between them.
In the round there is no beginning or end, so the plain stitches go into D equal gaps, one before each decrease. Worked flat, there is one more gap, so the row starts and ends with plain stitches and the shaping stays away from the edges, where it would get lost in a seam.
The plain stitches rarely divide exactly. When they do not, some gaps get one extra stitch. The calculator puts the longer gaps first so the instructions read as two simple repeats, for example "[K10, K2tog] 3 times, [K9, K2tog] 5 times, K9". No two gaps ever differ by more than one stitch.
For crochet, the same spacing is written with sc2tog, hdc2tog or dc2tog, and you can switch to UK names (dc2tog, htr2tog, tr2tog). On a wrong-side knit row, use P2tog.
Worked example
You have 100 stitches and want 92, so 8 decreases. They use 16 stitches, leaving 84 plain. Worked flat there are 9 gaps: 84 / 9 is 9 with 3 left over, so three gaps get 10. The row is: [K10, K2tog] 3 times, [K9, K2tog] 5 times, K9. In crochet with single crochet it reads: [Sc in next 10 sts, sc2tog] 3 times, [sc in next 9 sts, sc2tog] 5 times, sc in next 9 sts.
Common mistakes
- Counting the decrease as one stitch. K2tog uses two stitches from the left needle, so the plain stitches are fewer than you think.
- Using the flat spacing in the round. Worked flat, the last group of plain stitches would sit next to the first, giving a gap twice as long at the start of the round.
- Mixing US and UK crochet terms. A UK dc2tog is a US sc2tog; use the switch so the instructions match your pattern.
- Asking for more decreases than half the stitches. Each decrease needs two stitches, so 40 stitches allow at most 20 decreases in one row.
Last checked October 2026 against standard quilting and knitting math. Found a mistake? Tell us and we’ll fix it.