Sewing Machine Settings Guide
Needle size, type, stitch length and thread by fabric. The metric needle number is literally the blade width in hundredths of a millimetre.
Stitch length, both ways round
A European machine is marked in millimetres per stitch and an American pattern is written in stitches per inch, and the two run in opposite directions: a bigger number on one dial is a smaller number on the other. Type into either.
Every needle size, and what the numbers mean
The fabric picker gives you one row of this table. Here is the whole of it, because the useful move at the shop is usually the reverse lookup: you have a packet in your hand and want to know what it is for.
| Metric | US | Blade | Suits |
|---|---|---|---|
| 60 | 8 | 0.60 mm | Silk, chiffon, fine voile |
| 65 | 9 | 0.65 mm | — |
| 70 | 10 | 0.70 mm | — |
| 75 | 11 | 0.75 mm | Jersey and light knits; Lycra, swimwear, activewear |
| 80 | 12 | 0.80 mm | Quilting cotton, poplin; Linen |
| 90 | 14 | 0.90 mm | Fleece and sweatshirting; Leather and vinyl; Topstitching |
| 100 | 16 | 1.00 mm | Denim and canvas |
| 110 | 18 | 1.10 mm | Upholstery and heavy canvas |
| 120 | 19 | 1.20 mm | — |
| Point type | What it is for | Fabrics here |
|---|---|---|
| Universal | A slightly rounded point. Wovens and the easier knits. | Quilting cotton, poplin; Linen |
| Ballpoint / jersey | Pushes between knit loops instead of piercing them. Stops skipped stitches and holes in knits. | Jersey and light knits; Fleece and sweatshirting |
| Stretch | For very elastic fabric and anything with elastane. A deeper scarf prevents skipped stitches. | Lycra, swimwear, activewear |
| Microtex / sharp | A very fine point for silk, microfibre and tightly woven cotton. Gives the straightest stitch line. | Silk, chiffon, fine voile |
| Jeans / denim | A stiff blade and sharp point that will go through several layers without deflecting. | Denim and canvas; Upholstery and heavy canvas |
| Leather | A cutting wedge. Never use on fabric — it slices the threads. | Leather and vinyl |
| Topstitch | An oversized eye for thick thread. The fix when heavy thread keeps shredding. | Topstitching |
The needle number is the needle
The metric size is not a code — it is the blade diameter in hundredths of a millimetre. An 80 needle is 0.80mm thick. That is the whole system, and once you know it the numbers stop needing to be memorised.
| Metric | American | Blade | (metric − 20) ÷ 5 |
|---|---|---|---|
| 60 | 8 | 0.60mm | 8 |
| 65 | 9 | 0.65mm | 9 |
| 70 | 10 | 0.70mm | 10 |
| 75 | 11 | 0.75mm | 11 |
| 80 | 12 | 0.80mm | 12 |
| 90 | 14 | 0.90mm | 14 |
| 100 | 16 | 1.00mm | 16 |
| 110 | 18 | 1.10mm | 18 |
| 120 | 19 | 1.20mm | 20 — off by one |
The two scales are related by (metric − 20) ÷ 5, which is exactly right for eight of the nine common sizes and off by one at the largest, where 120 pairs with 19 rather than the 20 the formula gives. Worth knowing as a pattern; look it up rather than relying on it at the top of the range.
Needle type matters more than size
| Type | What it is for |
|---|---|
| Universal | A slightly rounded point. Wovens and the easier knits. |
| Ballpoint / jersey | Pushes between knit loops instead of piercing them. Stops skipped stitches and holes in knits. |
| Stretch | For very elastic fabric and anything with elastane. A deeper scarf prevents skipped stitches. |
| Microtex / sharp | A very fine point for silk, microfibre and tightly woven cotton. Gives the straightest stitch line. |
| Jeans / denim | A stiff blade and sharp point that will go through several layers without deflecting. |
| Leather | A cutting wedge. Never use on fabric — it slices the threads. |
| Topstitch | An oversized eye for thick thread. The fix when heavy thread keeps shredding. |
Skipped stitches in a knit are almost always the needle type, not the tension. A universal needle pierces the loops of a knit instead of sliding between them, which cuts them and skips stitches. A ballpoint or stretch needle costs about a pound and fixes it instantly. A needle lasts roughly eight hours of sewing and then blunts, invisibly.
Stitch length
Modern machines are marked in millimetres; older machines and older patterns use stitches per inch. The two are exact reciprocals of 25.4, so a longer stitch means fewer of them:
| Millimetres | Stitches per inch | Used for |
|---|---|---|
| 1.5mm | 16.93 | Fine fabric, tight curves |
| 2mm | 12.70 | Silk and lightweight wovens |
| 2.5mm | 10.16 | The default for most sewing |
| 3mm | 8.47 | Heavier fabric, knits, fleece |
| 3.5mm | 7.26 | Topstitching, denim, leather |
| 4mm | 6.35 | Basting and gathering |
| 5mm | 5.08 | Basting and gathering |
Thicker fabric wants a longer stitch. A short stitch in heavy fabric perforates it, packs too much thread into a small distance and puckers the seam. A long stitch in fine fabric has nothing holding it and the seam gapes. And a stitch under about 1.5mm is effectively a cutting line — it is very hard to unpick and it weakens the fabric.
Thread numbering runs both ways at once
Two scales describe one property and they point in opposite directions, which is a reliable source of confusion:
- Weight (wt) gets FINER as the number rises. 50wt is thinner than 30wt. Piecing cotton is 50wt; topstitching thread is 30wt or heavier.
- Tex gets THICKER as the number rises, because it is simply the weight in grams of 1000 metres. Tex 40 is twice the mass per length of Tex 20.
- They cannot be converted reliably, because weight numbering is not standardised between manufacturers — one company's 40wt is another's 50. Compare within a brand, or hold the two threads side by side.
- Match thread to fabric, not to ambition. All-purpose polyester handles almost everything. Cotton thread has no stretch and will snap in a knit seam.
Test on the real thing
Every setting here is a starting point. Machines differ, fabric bolts differ, and the only real test is a doubled scrap of the actual fabric — not a single layer, and not a different fabric. Sew a few inches, look at both sides, and adjust from there. It takes a minute and saves unpicking a finished seam.
How to use
- Pick the fabric and take the settings as a starting point.
- Change the needle TYPE before worrying about the size.
- Longer stitches for thicker fabric, shorter for finer.
- Test on a doubled scrap of the real fabric, never a single layer.
Frequently asked questions
What do the two numbers on a sewing needle mean?
They are the same size in two systems. The metric number is the blade diameter in hundredths of a millimetre, so an 80 needle is 0.80mm thick. The American number is a separate scale running 8 to 19. A packet marked 80/12 is one needle described twice.
How do I convert needle sizes?
The American size is very nearly the metric size minus 20, divided by 5. That is exactly right for eight of the nine common sizes and off by one at the largest, where 120 pairs with 19 rather than the 20 the formula gives. Useful as a pattern, but look the size up rather than relying on it at the top of the range.
What needle should I use for jersey or knit fabric?
A ballpoint or stretch needle, in a 75 or 80. A universal needle has a point sharp enough to pierce the loops of a knit rather than sliding between them, which cuts them and produces skipped stitches or small holes along the seam. Changing the needle type fixes it instantly.
Why does my machine skip stitches?
Almost always the needle: blunt, bent, in the wrong way round, not pushed fully up into the clamp, or the wrong type for the fabric. Tension has very little to do with it. Fit a new needle of the right type before adjusting anything else.
How often should I change the needle?
Roughly every eight hours of sewing, or at the start of any project you care about. Needles blunt gradually and invisibly, so there is no moment where it obviously fails — it just gets slightly worse until the stitches look wrong. They cost very little and replacing one is faster than diagnosing anything.
What stitch length should I use?
About 2.5mm for most sewing, which is the default on almost every machine. Go shorter, around 1.8 to 2mm, for fine fabric and tight curves. Go longer, 3 to 3.5mm, for denim, fleece, leather and topstitching. Basting and gathering want 4 to 5mm.
How do I convert stitch length to stitches per inch?
Divide 25.4 by the length in millimetres, since that is how many millimetres are in an inch. The default 2.5mm is 10.16 stitches per inch, and 10 stitches per inch is 2.54mm. The two units are exact reciprocals so the conversion runs both ways without loss.
Why does thicker fabric need a longer stitch?
Because a short stitch packs too much thread into too little distance, which perforates the fabric and puckers the seam. A long stitch in fine fabric has the opposite problem — too little holding it, so the seam gapes. Below about 1.5mm the stitching line is effectively a cutting line and is very hard to unpick.
Is 50wt thread thicker or thinner than 30wt?
Thinner. Weight numbering gets finer as the number rises, which is backwards from most measurements. 50wt is standard piecing cotton; 30wt is noticeably thicker and used for topstitching and quilting where the stitch is meant to show.
What is Tex and how does it relate to weight?
Tex is the weight in grams of 1000 metres of thread, so it gets THICKER as the number rises — the opposite direction to weight numbering. Two scales for one property pointing opposite ways is a reliable source of confusion, and they cannot be converted reliably because weight numbering is not standardised between manufacturers.
Can I use cotton thread on knits?
Better not to. Cotton thread has essentially no stretch, so when the knit seam stretches the thread is what gives, and it snaps. All-purpose polyester has enough give to survive it, which is why it is the default for anything with stretch in it.
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