Zigzag Stitch, Explained by Width and Length
Two dials control everything about a zigzag: how wide it swings and how far apart the swings sit. Get those right and the stitch stops looking like an accident.
What it is & when you need it
A zigzag is a straight stitch with a sideways wobble, and that single difference is why it does jobs a straight stitch cannot: it stretches with a knit, it bridges a raw edge so the fibres cannot fray, and it can be built up into a satin-like bar of thread.
The two settings interact, which is where most confusion comes from. Width decides how far the needle travels sideways; length decides how far the fabric travels forwards between swings. Wide and long gives you an open net for appliqué or a buttonhole. Narrow and dense gives you a satin column that looks deliberate.
Once you think in terms of density rather than two separate dials, the stitch becomes predictable. Every use below is really the same decision: how much thread do you want sitting on this fabric, and does it need to move with it.
How to choose the right one
Read this as a starting point, then test on two folded layers of the real fabric. Density is what makes the difference between a zigzag that finishes an edge cleanly and one that chews the cloth or leaves it flapping open.
| Job | Width | Length |
|---|---|---|
| Finishing a raw woven edge | 3-4 mm | 1.5-2 mm |
| Stretching a knit seam | 1-1.5 mm | 1.5-2 mm |
| Appliqué or decorative outline | 2-3 mm | 0.4-0.6 mm |
| Bartack or reinforced buttonhole | 2.5-3 mm | 0.3-0.5 mm |
| Sewing on elastic | 2-3 mm | 2-2.5 mm |
What you'll need
Standard zigzag foot
The wider sole supports the fabric while the needle swings, which is what stops lightweight cloth being sucked down with it.
Ballpoint needle for knits, sharp for wovens
A zigzag punches more holes per centimetre than a straight seam, so the wrong point cuts yarns and the seam runs.
Two-layer test scrap of the real fabric
Test width, length and tension together on the fold, because a zigzag shows up tension faults far more obviously than a straight seam.
Stabiliser, tearaway or wash-away
Under the dense settings, the fabric needs support or the row cockles and the stitches sink into the cloth.
Fabric pen and ruler
A drawn line gives the swing something to land on, which is how you keep an appliqué outline smooth.
All-purpose thread, plus a heavier top thread for trim
40wt or cotton variegated thread on top turns a functional zigzag into an intentional decorative edge.
How to do it, step by step
- 1
Decide what the stitch has to do
Choose one of three jobs: finish an edge, allow for stretch, or sit on the surface as decoration. Each wants a different density, and the dials follow from the choice rather than the other way round.
Write the settings on a card taped inside your machine box once you have tested them, so the next project starts from your fabric rather than from the manual.
- 2
Set width first, then length
Width is measured in millimetres of sideways travel. Set it so the needle clears the edge you are finishing by a thread, and no wider than that: excess width is what shreds fine fabric.
Then set length. Small numbers pack the swings together into a solid band; larger numbers open them into a net. Change only one dial at a time when you are testing.
- 3
Test on the folded scrap
Sew 4 cm on two layers, exactly as the seam will be, then look at both faces and give the seam a gentle pull.
A good finishing zigzag hugs the edge without tunnelling. A good stretch zigzag recovers when you release it and does not pop when you pull the seam open.
- 4
Align the edge at the left swing
For edge finishing, let the fabric edge meet the needle at the leftmost point of the swing, so the right swing lands on the cloth. Guides on the foot plate show you where that is.
If the needle falls off the edge every other stitch, shift the fabric a millimetre in, or narrow the width rather than steering as you sew.
- 5
Sew slowly and let the needle do the work
A zigzag is the one stitch where speed genuinely costs you accuracy. The needle is travelling sideways at full swing, and hurrying makes it deflect, which shows as a wandering line.
Keep steady light feed from behind the foot. On fine fabric, lay a strip of tissue or wash-away stabiliser under the seam to stop the puckering that speed causes.
- 6
Lock the ends properly
A zigzag frays out more visibly than a straight seam because the loops are exposed. Backtrack two or three stitches at both ends, or set the machine to a straight stitch for the last two.
On a decorative edge, stop with the needle at the centre position so the row ends symmetrically instead of half-swung to one side.
- 7
Press and check the recovery
Press with a hot iron through the stitch to set it, then stretch the seam sideways. A knit seam should open and close with the fabric and return without a wavy seam line.
If the seam ripples after stretching, the stitch was too dense for the movement it needs. Lengthen it slightly and test again on the scrap.
Pro tips
- When a zigzag looks chewed at the edge, drop the width a step before you touch the tension. Most chewing is the needle travelling further than the fabric can support.
- Use the three-needle zigzag variants for seams that take real abuse, such as activewear side seams and bag gussets, because the three columns share the load.
- For satin-density bars and bartacks, slow the machine right down or use the handwheel, and put stabiliser underneath. Density without support is what makes a fabric tunnel.
- Keep a scrap card with your tested settings per fabric, and sew a test block on it before each project. It takes ninety seconds and prevents a whole afternoon of unpicking.
- A longer stitch length with a wide width is a legitimate decorative trim on hems and cuffs, so do not assume wide always means functional.
Common mistakes (and how to fix them)
The fabric is cut or shredded along the finished edge.
The needle is falling past the edge on the left swing, or the width is too great for the cloth. Narrow the width and reposition the fabric so both swings land on the material.
Loops of top thread appear on the underside.
Top tension is too loose for the sideways travel, or the foot was down while threading. Increase top tension a step, re-thread with the foot raised, and retest on the fold.
The row tunnels and the fabric gathers under it.
The stitch is too dense for the fabric weight, with no support underneath. Lengthen it slightly and add tearaway or wash-away stabiliser so the cloth cannot be pulled up around the thread.
The seam splits when the knit is stretched.
You used a narrow dense zigzag that cannot travel. Widen the length to about two millimetres, or switch to a proper stretch stitch, and check the needle is a ballpoint.
Frequently asked questions
What is the best zigzag setting for finishing edges?
A width of three to four millimetres with a length of one and a half to two millimetres works on most woven fabrics. Place the edge so the left swing just drops off it, and the right swing sits on the cloth, which locks the fibres without cutting them.
Can a zigzag replace an overlocker on knits?
For seam finishing it is close, and a three-needle overcast stitch is better again. A zigzag cannot trim the edge, so the allowance has to be cut evenly first. For a sewn knit seam that needs to stretch, use a stretch stitch or a narrow long zigzag.
Why does my zigzag stitch skip on one side only?
The needle is deflecting sideways as it reaches the far swing, usually because it is blunt, bent or too fine for the fabric. A curved-shank foot on a straight-shank machine also shifts the needle off centre, so check the foot matches the machine.
How tight should zigzag tension be?
Snug but not punishing. The stitches should interlock inside the fabric layers rather than showing one thread on the surface. Dense decorative settings want slightly looser top tension than finishing settings, because the thread is sitting on the face instead of sinking in.
What width do I need for a buttonhole?
Around two and a half to three millimetres for a normal button, with a length of about half a millimetre for the bars. Measure against your actual button: the width should be slightly narrower than the button's shoulder so the hole grips it.
Written by Bobbin & Form Editorial Team
Home sewists & machine-embroidery practitioners
Reviewed by Marie Delacroix
Custom sewist & machine-embroidery technician, 15 years at the machine
Steps were written and re-tested on real fabric by our team and reviewed by an independent sewing and embroidery professional. Results vary with your machine, fabric and supplies, so always run a scrap test on the same materials before stitching a finished piece. Nothing here is sponsored — when we link to a calculator or product it is because it is genuinely useful.
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