Increase and decrease calculator

Patterns say "decrease 8 stitches evenly across the round" and leave the arithmetic to you, which is fine until the numbers refuse to divide. One hundred stitches and eight decreases give twelve and a half stitches between each one, and there is no half stitch — so the round is worked in two run lengths, some longer and some shorter, and the difference is invisible in the finished fabric. This page works out how many of each and writes the round out for you.

How it is worked out

runs = stitches ÷ changes, with the remainder spread one extra stitch at a time

Dividing gives the base run length and a remainder. The remainder is how many runs get one extra stitch, so no two runs ever differ by more than a single stitch. Decreases are handled before the division rather than after it: a k2tog consumes two stitches and returns one, so those stitches leave the pool before the spacing is worked out.

Source: integer division with the remainder distributed

Questions people ask

Which run should come first?

It rarely matters, and this page puts the longer runs first. If the round begins at a visible place — the centre back of a hat, the start of a sleeve — you may prefer to start with half of a plain run so that no shaping lands exactly at the join. Splitting the first run in two and working the other half at the end does that without changing any other number.

Does this assume a particular increase?

It assumes an increase that adds a stitch without consuming one — a make-one, a yarn over, a lifted increase — and a decrease that consumes two and returns one, which covers k2tog, ssk and p2tog. A knit-front-and-back consumes the stitch it works into, so treat one of the plain stitches in each run as the one you increase into and the counts still hold.

Why does the tool refuse some numbers?

Because they cannot be worked. Four k2tog across ten stitches would eat eight of them and leave two to spread between four decreases, which is not a round anybody can knit. The refusal is the honest answer: either make fewer changes in this round, or split them across two rounds.

Can I use this for crochet?

For increases, yes — the arithmetic is the same and an increase is usually two stitches into one stitch, which adds one without consuming extra. For decreases, a sc2tog also takes two and gives one, so the decrease option holds as well; only the abbreviation on screen is a knitting one.

How do I spread shaping over several rounds instead of one?

Run this once per shaping round with the count you will have at the time, which changes after every round. For a raglan or a hat crown the interval between rounds is set by the depth you need rather than by the stitch count, so it is a separate decision from the spacing this page gives.

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