What "evenly across the row" really means
Patterns use this phrase constantly, and almost never explain it. All it means is: space your increases or decreases out so they're spread across the whole row rather than bunched together, which would create a visible pucker or flare in one spot.
The arithmetic is simple enough once you see it. Divide the stitches you have by the number of changes you need to make, and that tells you how big each group should be. Where it doesn't divide neatly — which is most of the time — some groups get one extra stitch, and the calculator above sorts that out for you and writes it as an instruction you can follow stitch by stitch.
A small thing that makes it look professional: when working flat, keep two or three plain stitches at each end of the row. Shaping worked right at the edge makes seaming and picking up stitches fiddly, and it shows. The instructions above already allow for this on flat rows.
Which increase or decrease should I use?
For knitting, k2tog is the everyday decrease and leans to the right; ssk leans left, and pairing the two on either side of a sleeve or raglan gives a tidy mirrored line. For increases, m1 is nearly invisible and good for spreading across a row, while kfb is easier to work but leaves a small bar — fine for ribbing and casual pieces.
For crochet, decrease by working two stitches together — sc2tog or dc2tog depending on the stitch — and increase by working two stitches into the same stitch. Because crochet stitches are taller and wider than knit stitches, shaping shows more, so spreading it evenly matters even more here.
Working in the round
In the round there are no edges to protect, so the changes are spaced right around with no plain stitches held back. The calculator adjusts for this when you choose "in the round" — you'll notice the groups come out slightly different from the flat version of the same numbers.
Marking as you go
Stitch markers are worth the small cost here. Before you start the row, place a marker every time a change should happen — then work the row without counting, simply doing the increase or decrease when you reach each marker. This is far more forgiving than counting to nine, twice, while somebody talks to you.
Questions we're often asked
How do I decrease evenly across a row?
Divide the number of stitches you have by the number of decreases you need. That gives the size of each group. Work that many stitches minus two, then a decrease, and repeat across the row. Where the numbers don't divide evenly, some groups take one extra stitch — the calculator above writes out exactly where.
What does "k8, k2tog" mean?
Knit eight stitches normally, then knit the next two together as one. That uses ten stitches and produces nine, so repeating it across the row reduces your count by one stitch for each repeat.
Should I decrease on a right side or wrong side row?
Right side rows, unless the pattern says otherwise. Decreases worked on the right side sit neatly and are far easier to see and count as you go.
How do I increase evenly for a sleeve?
Use the second calculator above. Give it your starting and ending stitch counts and the number of rows you have to get there, and it will tell you how often to work the increase row — for instance "increase 1 stitch at each end every 5th row, 15 times".
Does this work for crochet as well as knitting?
Yes — choose crochet at the top and the instructions use crochet terms. The spacing maths is identical; only the stitch names change.