Needle size follows thread size. Get the pairing wrong and no amount of tension adjustment will save the seam.
The principle. The needle has to make a hole big enough for the thread to pass through twice — down and back — without chafing, but no bigger than it needs to be. Too fine and the thread frays and breaks. Too coarse and you leave visible holes and a weak seam.
Thread to needle
Published as ranges, because that is how the thread makers give them. Within a range, go finer for a tight weave and coarser for something dense or layered.
| Thread (Tex) | Commercial | Workable range | Usual choice | Typical work |
|---|---|---|---|---|
| T35 | #33 | 80/12 – 90/14 | 90/14 | Very light work, linings, fine detail. Rare in upholstery. |
| T45 | #46 | 90/14 – 100/16 | 100/16 | Light upholstery, thin leather, cushion interiors, delicate work. |
| T70 | #69 | 100/16 – 130/21 | 110/18 | The standard upholstery thread. Sofas, chairs, most seams. The heaviest most domestic machines will manage. |
| T90 | #92 | 110/18 – 140/22 | 110/18 or 125/20 | Automotive and vehicle trim, vinyl seating, heavier furniture. Needs an industrial machine. |
| T135 | #138 | 125/20 – 180/24 | 130/21 or 140/22 | Visible top stitching, leather, decorative seams where the stitch is meant to be seen. |
| T210 | #207 | 140/22 – 200/25 | 160/23 | Heavy leather, bold contrast stitching, hard-use seating. |
| T270 | #277 | 180/24 – 230/26 | 180/24 or 200/25 | Saddlery, very heavy leather, deliberate feature stitching. |
| T350 | #346 | 220/26 – 250/27 | 230/26 | Harness work. Beyond most upholstery machines. |
Published charts do not agree with each other. The two most widely cited differ by roughly one size step across the middle of the range — one recommends 125/20 to 140/22 for T135, the other 140/22 to 180/24 for the same thread. Neither is wrong. Needle choice depends on the material as much as the thread, so there is a workable band rather than a single correct answer. The ranges above span both charts; the usual column is where most people land.
And not every size is stocked everywhere. Walking foot needles are often sold in packs of Singer sizes 18, 20, 21, 23 and 24 — metric 110, 125, 130, 160 and 180. So a chart telling you to fit a 140/22 or a 200/25 may be sending you after something your usual supplier does not carry. Where that happens, take the nearest stocked size within the range and test on an offcut. The band exists for exactly this reason.
Reading needle sizes
Needles carry two numbers, such as 110/18. They are two names for one needle, not two measurements.
The first is NM, the metric number: the blade diameter in hundredths of a millimetre, so 110 means 1.10 mm. Schmetz specify that it is measured above the scarf or the short groove, and not at any reinforced part of the blade — which is why a reinforced needle can measure thicker than its number in places. The system was fixed in 1942 to replace some forty competing ones.
The second is the older American, or Singer, size. It is an arbitrary scale rather than a measurement, but it maps consistently: NM 110 is always an 18.
Needle systems
A system is a shank diameter and a length. It has nothing to do with size. A needle of the right size in the wrong system will not fit, or will not time correctly.
- 135×16 and 135×17 — the walking foot system, and the one most upholsterers use. The two are interchangeable: same shank, same length, different point. 135×16 is the leather point, 135×17 the round point for cloth. Also sold as DP×16 and DP×17.
- 134 — many flat-bed lockstitch machines. Also sold as 135×5, 135×7 and DP×5.
- DB×1 — common on lighter industrial lockstitch heads. Watch this one: the shank is 1.63 mm up to 110/18, and above that size the same needle is made on a 2.00 mm shank and becomes system 134. To stay on the narrow shank at larger sizes you need system 1738A.
- 190 (190R, MTX190) — Pfaff and Pfaff-pattern industrial machines. 2.00 mm shank.
- 130/705H — domestic machines, identifiable by the flat on the shank. Also sold as HA×1 and 15×1.
Your machine’s manual states its system. Failing that, it is usually stamped on the packet of whatever is in the machine now.
Round point or leather point
This matters more than most people expect.
A round point (R) pushes between the yarns of a woven cloth without cutting them. Use it on anything woven. Put a leather point through woven cloth and you cut the yarns, which weakens the seam along its whole length.
A leather point is a cutting point, ground to slice a small clean incision rather than punch a hole. The grind determines which way the cut lies and therefore how the stitches sit — LR is the common general-purpose leather point and gives a neat line slightly angled to the seam.
Vinyl is the awkward one. It behaves like leather to the needle but is usually backed with a woven scrim, and a leather point cuts that backing. Groz-Beckert describe their R point as suiting woven fabrics, leather, artificial leather and coated fabrics alike, which is the manufacturer’s way of saying a round point is a defensible choice on vinyl. Many trimmers use one for exactly that reason. Test on an offcut of the actual material before committing on a customer’s job.
Change needles more often than you think
A needle blunts long before it looks blunt. A blunted point pushes material down rather than piercing it, which is a common cause of skipped stitches and puckering that gets blamed on tension. If a machine that was sewing well starts misbehaving, put a new needle in before you touch anything else. It is the cheapest thing in the workshop and the most frequent culprit.
You will see hour-counts quoted for this — change it every eight hours and so on. Those come from garment production, where a machine runs all day on fine cloth and a slightly blunt point shows at once. Upholstery is not that. You sew a seam and go back to the bench, and the needle is a heavier thing to begin with. Change it when the work tells you: skipped stitches, a change in the sound, snagging in the face, or straight after it has met a tack, a staple or the plate.
Want this worked out for you? The thread and needle selector pairs the thread, needle, point and stitch length in three questions.
Also in this section: thread · machines · troubleshooting · setup · everything.
Sizing is standardised, so these numbers hold wherever you work. Manufacturers do vary slightly at the margins, though — if your thread supplier publishes a chart for their own product, it beats any general table including this one.