Gauge calculator
Crochet a 15 × 15 cm swatch in the pattern stitch, then measure 10 cm (4 in) across the middle and count your stitches.
Check your tension
Compare your swatch with the pattern's gauge — both counted over the same 10 cm / 4 in.
How many stitches to start?
Use your gauge (from the swatch above) to work out a starting stitch count for any width.
Add any turning or foundation chains your pattern calls for on top of this.