How to Sew a Straight Line: Beginner Practice for a 15 mm Seam

A straight seam comes from a steady guide, not from gripping the fabric and trying to steer every stitch. Start slowly on a scrap so you can focus on where the fabric edge is going.

Choose the seam allowance first

For many woven projects, 15 mm (1.5 cm) is a useful practice allowance. Some patterns use a different amount, so always check the instructions for the project you are making. Five-eighths of an inch is just under 16 mm; treat the two as close only when the pattern allows it.

Watch the guide, not the needle

Find the 15 mm marking on your needle plate. If your plate has imperial markings or no clear guide, place a small piece of low-tack tape parallel to the presser foot at the right distance. Keep the raw edge aligned with that guide as the feed dogs move the fabric.

Keep the fabric relaxed

Let the machine feed the fabric; do not pull it from behind or push it from the front. Sew slowly enough to keep your edge aligned, then check the seam on both sides. If it drifts, adjust your guide or speed and try another line. A slightly wobbly practice seam is useful information, not a failed project.