Knitting Blanket Border Calculator

Picking up along the cast-on/bind-off edges vs the side edges

Along the cast-on and bind-off edges, you're picking up directly from existing stitches, so the count follows your body stitch gauge one-to-one. Along the two side edges you're picking up from row-ends instead, and a row is almost never the same height as a picked-up stitch is wide — stockinette rows are noticeably shorter and denser than a stitch is wide, so picking up one stitch per row-end would flute and ruffle the edge. The standard fix is to pick up fewer stitches than there are rows: roughly 3 out of every 4 rows for a stockinette or ribbed border, a bit fewer (about 2 out of 3) for garter stitch, since garter rows are shorter still.

Why the corners use paired increases, every round

Working a picked-up border in the round (all four sides on one circular needle, with a stitch marker at each corner) lets you turn each 90° corner with a fixed increase — typically a yarn-over on each side of the corner stitch, or a lifted increase like kfb — worked at every corner marker on every round. Like a crochet corner, a knit corner is a fixed angle rather than a curve, so this rule doesn't need to grow as the border gets thicker; only the straight-side stitch counts increase round to round, because each new round sits on a slightly larger rectangle than the one before it.

Keep it honest with a swatch

Pick-up ratios are a solid starting guideline, not a guarantee — yarn with a lot of drape or a very open lace body can behave differently than these defaults assume. After the first round, lay the piece flat: if the border cups inward, you've picked up too few stitches on that edge; if it ruffles or waves, too many. It's easier to rip back one round and adjust than to block a persistently rippled border flat after the fact.