Crochet Increase Calculator

The placement model

The calculator models a standard one-stitch increase as two stitches worked into one source stitch. A standard decrease works two adjacent source stitches together as one. Therefore, with N starting stitches and K changes, an increase finishes with N + K stitches and a decrease with N − K. In target mode, the difference between the target and N determines the operation and K. A target equal to the starting count produces a valid no-change plan.

For a flat row, let EL and ER be the reserved left- and right-edge stitches. The available section contains:

M = N − EL − ER

Each increase occupies a source width c = 1; each decrease occupies c = 2 adjacent source stitches. For action j, numbered from 0 to K − 1, the calculator finds the midpoint of its share of the available section:

x = (j + 0.5) × M ÷ K

It places the zero-based action start at round_half_up(x − c ÷ 2), constrained to 0…M − c, then adds the reserved left edge and converts the position to one-based numbering. This keeps both reserved edges untouched and places actions around group midpoints instead of pretending that a remainder can be split into fractional stitches.

In a round, action j starts at zero-based cyclic position floor(j × M ÷ K). The displayed positions are one-based from the round marker. A decrease consumes that stitch and the next; feasibility checks prevent a decrease from crossing the marker.

Worked row example with reserved edges

Start with 24 stitches, reserve 2 stitches on the left and 3 on the right, and make 5 increases. The available section is 24 − 2 − 3 = 19 stitches. Standard increases have width 1. The midpoint calculation places them in original stitches 4, 8, 12, 16 and 20. Stitches 1–2 and 22–24 remain untouched, and the row finishes with 29 stitches. If “sc” is selected, each action is worded as working 2 sc in the indicated stitch; the positions are unchanged.

Worked round decrease

Start with 30 stitches and target 24 in a round. Target mode derives 6 decreases. Cyclic floor positions split the 30-stitch round into six equal sections, so the decreases begin at original stitches 1, 6, 11, 16, 21 and 26, consuming each listed stitch and the next. The six actions remove six stitches and the completed round contains 24 stitches.

Check the plan before crocheting

• All positions refer to the original source stitches. Mark them before working if changing counts would make recounting confusing.
• Edge reserves apply only to rows and are not shaping instructions. Turning chains or joins belong in the starting count only when the pattern counts them as stitches.
• Stitch wording changes the text, not the technique. Use the pattern’s definition of an increase, decrease, invisible decrease, turning chain or custom stitch.
• Rotating an entire round sequence around its marker is mathematically equivalent. Across repeated rounds, a designer may deliberately offset shaping to avoid visible corners.
• Pattern repeats, lace, cables, colourwork, garment seams and structural shaping may require deliberately uneven placement. Explicit pattern directions take priority over this neutral spacing model.