Where do I get my row gauge?

From a swatch: count the rows over 4 inches or 10 cm, ideally after blocking. The Gauge from Swatch calculator works it out for you.

Why does row gauge matter more than stitch gauge for length?

Length runs up the rows, so it is row gauge that turns a measurement into a row count. Stitch gauge governs width instead.

Yes. Read "rows" as your crochet rows and enter your crochet row gauge — the length-to-rows math is the same.

Turn a length into a row count using your row gauge — inches or cm.

Row gaugerowsGauge measuredLength to knitLength unit

Knit 126 rows

At 7 rows per inch.

Enter your row gauge — the number of rows in your swatch over 4 inches or 10 cm — and pick which one you measured over.
Enter the length you want to knit and choose inches or centimetres.
Read how many rows to work to reach that length.
Use it for sleeve lengths, body length to the underarm, or any straight run where the pattern gives a length, not a row count.

Row gauge and length can use different units here — a per-10-cm gauge with an inch length works fine; everything is converted internally.
Get your row gauge from a blocked swatch with the Gauge from Swatch calculator, in the stitch pattern you will actually knit.
Round to a whole number of pattern repeats if your stitch pattern needs it — the row count is a target, not a hard rule.

Where do I get my row gauge?: From a swatch: count the rows over 4 inches or 10 cm, ideally after blocking. The Gauge from Swatch calculator works it out for you.
Why does row gauge matter more than stitch gauge for length?: Length runs up the rows, so it is row gauge that turns a measurement into a row count. Stitch gauge governs width instead.
Does this work for crochet?: Yes. Read "rows" as your crochet rows and enter your crochet row gauge — the length-to-rows math is the same.