For most seams on a sewing machine, set the stitch length to 2.0 to 2.5 mm (about 10 to 13 stitches per inch). Go shorter, toward 2.0 mm, on lightweight fabric that puckers. Lengthen to about 3.5 mm for topstitching, and use 4 to 6 mm for basting and gathering. On most machines the dial number is the stitch length in millimeters, and a higher number means a longer stitch.

Stitch length chart by task

Task Stitch length Stitches per inch (approx.)
Seams in lightweight fabric that tends to pucker 2.0 mm 13
Everyday seams in woven fabric 2.0 to 2.5 mm 10 to 13
Seams in heavy denim about 2.5 mm about 10
Topstitching and jeans hems about 3.5 mm (slightly longer than the seam) about 7
Machine basting 4.0 mm or longer 6 or fewer
Gathering, or basting at the longest setting up to 6 mm about 4
Seams in knit fabric Use a narrow zigzag or stretch stitch, not just a straight stitch n/a
Sewing on a button 0 (fabric isn’t fed) n/a

The seam, gathering and basting lengths come from the Home Sewing Association’s straight-stitch guideline, the denim figure from its denim guideline (about 10 stitches per inch for heavy denim), and the 3.5 mm topstitch from its jeans-hemming guideline. Brother’s basting instructions use 4.0 mm with the tension loosened. For quilt piecing and quilting lines, use the quilting stitch-length guide instead.

Treat the chart as a starting point. Thread weight, needle and fabric thickness still decide the final setting, so sew a sample on scrap from the same fabric first.

Read the dial correctly

Brother’s stitch-length instructions explain millimeter-marked dials, longer stitches at higher numbers and no forward feeding at zero for the covered machines. Other machines can use different scales or preset settings. Read the model manual rather than assuming every dial number is a millimeter.

Length and width are separate. For zigzag, width describes side-to-side movement while length describes forward spacing. On some machines a width control also changes straight-stitch needle position. A decorative or stretch-stitch program may impose its own adjustment range; a straight-stitch setting does not transfer directly to it.

Convert millimeters to stitches per inch

For an evenly fed straight stitch, the arithmetic is stitches per inch = 25.4 รท stitch length in millimeters.

Nominal length Calculated stitches per inch Meaning
2.0 mm 12.7 More penetrations per inch than 2.5 mm
2.5 mm 10.2 A reference point for comparing samples
3.0 mm 8.5 Fewer penetrations per inch than 2.5 mm
4.0 mm 6.4 More open spacing, often useful when a task calls for long removable stitches

These are calculated values rounded to one decimal, not measured output from your machine. Feed slippage, bulky crossings and the stitch program can change actual spacing. Count complete stitch intervals over a measured straight section if you need to check the result. Do not apply this formula to the total thread path of a zigzag or decorative pattern.

Diagnose puckering before changing the number

Coats’ seam-puckering guide separates tension-related puckering, crowded fabric structure, feeding effects and dimensional changes. Where densely packed stitches displace the fabric yarns, reducing stitch density can help; on a straight stitch that means a longer interval, not a shorter one. Excessive tension or mismatched feeding needs a different response.

Use scrap material for any unpicking or diagnostic trial. Keep the same thread, needle and layers while comparing two nearby permitted lengths. Inspect both sides after the sample relaxes. If both lengths pucker, investigate setup and material instead of repeatedly shortening the seam. If the seam looks sparse, lengthening it produces even fewer stitches; first decide whether the issue is density, tension or the intended design.

Coats’ stitch-type reference also distinguishes lockstitch from chain and overedge constructions. This matters for knits: changing the length of a straight lockstitch does not give it the same behavior as a different stitch structure.

Keep the successful sample

Label it with model, stitch program, length, width if relevant, needle, thread and material layers. Include any seam intersection you will cross. After temporary basting, restore the intended permanent-seam setting and make another sample before sewing the garment.

This chart is researched from manufacturer and sewing-industry guidance, not from stitch samples sewn for this site. The stitches-per-inch figures are arithmetic (25.4 divided by the length in millimeters), rounded.

Sources