Finding the right needle size in the Haystack pt.1

Review part two of three of Stuart’s guide to thread (part one) and needles.

There are far too many different sewing needles. Big ones, small ones; sharp ones, blunt ones; silver ones, gold ones. Tens of thousands of different kinds of sewing needles. And there are probably a half-dozen different names for any one sewing needle. So how do you get “the right” sewing needle? This article may give you enough information to search through the haystack for the proper needle size, system, and point for your application. Or it may give you a headache. We shall see.

I am not going to talk about hand sewing needles, special coatings, ganged needles (household double and triple needles) and specialty forming needles (hemstitch, pin-point, chenille, felting, etc.), but we will still have a huge amount of material to cover.

Let’s start with the basic anatomy of a machine sewing needle. You have probably seen this diagram twenty times before.

Your machine’s needle bar grasps the shank. The point pierces the fabric. Between them is the blade. A lockstitch needle has a long groove on one side of the blade and a scarf scooped out of the other side of the blade. A chainstitch needle will have long grooves on both sides of the blade. The thread will run down the long groove(s) and through the eye.

The three critical dimensions are the diameter (thickness) of the shank, the diameter of the blade, and the distance from the butt end of the shank to the top of the eye. The needle thread loop (needed by the bobbin hook or bottom thread loopers) forms immediately above the eye of the needle, and it must form at a fixed location relative to the body of the machine. So the butt-to-eye distance is critical, and the shank diameter determines if you can even get the needle into the machine in the first place. The distance from the eye to the tip of the point is, perhaps surprisingly, not a critical dimension although it does affect how the needle performs, as do the overall taper of the point and the shape of the very tip. The third critical dimension (blade diameter) is the subject of the next section.

Blade Diameter (The Size)
The “size” of a needle is the thickness of the blade. Some needles have tapered blades, other needles are enlarged around the eye, but some part of the blade will have a uniform diameter and this is what gets measured. Needle size affects two things: how large a hole is made in the fabric and how large a thread should be used. As a general rule, use the smallest needle and thread that are suitable for the job.

“Will the thread fit through the eye?” That is too simple a question about needle size. You will get stitching problems if the thread is either too big or too small for the needle. At first glance, many of these problems look like issues with poor tension adjustment or thread quality. The ideal thread diameter is about half the needle eye diameter. It should be small enough to slide freely in the long groove on the blade when pulled, but big enough not to buckle inside the long groove when pushed. The needle-to-thread size relationship has considerable tolerance, but you need to be aware that you can’t use a fine thread with a heavy needle just because it will fit through the eye.

Needle system design (see next section) also affects proper thread size. For example, topstitching needles have larger long grooves and eyes to accommodate a heavier thread than a normal needle of the same size.

There is a “home recipe” that works pretty well to evaluate a needle and thread combination without using any charts, graphs or mathematics. Take the needle out of the machine and thread it. Hold the thread taut, with your hands about a foot apart and the needle between them. Tilt the thread halfway between vertical and horizontal and twirl the needle around the thread briefly. Stop twirling. If the needle does not slide down the thread as the twirling stops, it is too small for the thread. If the needle just falls down the thread, it is too large. The needle should slide smoothly, but with some slight drag from the thread.

Once upon a time, there were hundreds of needle sizing systems. By one estimate, there were roughly 4,000 sizing systems, with up to 15 sizes per system. Every manufacturer had a sizing system, and some manufacturers had two or three! Fortunately, only two systems are still in wide-spread use: the Singer system and the metric system. Needles are usually marked with both sizes, so checking for the desired size is easy.

The metric needle sizing system, introduced in 1953, is very straightforward. The diameter of the needle is given in hundredths (percentage) of a millimeter. For example, a Nm 100 needle is 1 millimeter in diameter, while a Nm 50 needle is half a millimeter in diameter. (At least one source has confused Nm with nanometer, but nanometers are 10,000 times smaller!)

The Singer system, which the Japanese industry also adopted, uses somewhat arbitrary numbers. In the smaller sizes, each successive size is pretty close to 0.05 millimeters larger than the size before, but the increment is larger for the larger sizes. You can use either system, but it’s easier to read the actual size right off the metric size.

Here is a table of standard Singer and metric sizes covering light through extra-heavy sewing. I have come up with a recommendation for corresponding Tex thread sizes in the third column, but you (or your sewing contractor) should determine which needle size works best for your specific combination of fabric, thread, and seam. The fourth and fifth columns contain the extremes of possible thread sizes, based on various assumptions of needle system and thread construction* and you should not expect to work at the extreme values without testing.

[How annoying, Stuart’s chart won’t format. Until I can figure out why, see the 22 kb pdf]

There are some sewing machines designed for light-weight materials only, such as the Juki DDL-8700A or -5550A models. Needle size 75 is about the upper limit for these machines. The most common medium-duty sewing machines can work down into the light-duty range and up to about needle size 100 or 110. It takes a heavier machine to use larger needles. It’s not just a matter of power, either. The parts under the needle plate need to be compatible with the larger diameter needles and threads. The hook-to-needle timing and spacing is affected by blade diameter, and the raceway between the hook base and the basket (bobbin case holder) must be large enough to let the thread slide freely. Most heavy-duty machines have an upper limit somewhere around needle size 160.

As a matter of fact, Schmetz has introduced a line of needles (FHS) specifically designed not to require any hook spacing changes when changing needle sizes. General purpose sewing machines usually don’t require such changes, but the machines used in shoe manufacturing apparently have tight enough working tolerances to require a mechanic’s attention when changing needle sizes in the Nm 70 to 120 range. Schmetz is marketing this needle design as a production time-saver for that particular application. So it is possible you will run into a medium-duty machine that won’t reliably stitch with a small needle unless the hook spacing is changed (and obviously, changed back when the original needle size is restored).

Needles larger than size 160 or 180 are for extra-heavy sewing. Only the heaviest of sewn products (e.g., leather shoes, saddles, industrial cargo slings) would require the corresponding thread. Ordinary heavy-duty machines can’t handle them. So if you plan to topstitch denim with T-240 thread or larger, be aware it’s going to take a specialty machine with greater capacity than a normal “denim” heavy-duty machine. In fact, needle systems for conventional machines don’t offer sizes this large, as the blade would be larger than the shank that holds the needle in the machine!

There is a super-heavy range above Nm 250, but it’s not relevant in practice. Even within the monster-sized Singer class 7, almost all models are limited to Nm 250. I could not find a needle larger than Nm 300 (Singer 29) in production from any of the major needle manufacturers (and those were for sack-sewing and bag-closing machines). A Nm 300 needle is 3 millimeters across (significantly more than 1/16 of an inch), and wouldn’t look out of place in a box of nails.

While the metric and Singer needle sizes are used almost everywhere, there are a couple of niches where other needle sizing systems survive. The two main exceptions I encountered when researching this article were blindstitch (which has mostly converted to metric/Singer) and machine lace embroidery. If you have an archaic machine manual or engraved plate that uses some other sizing system, CTSUSA has a size cross-reference chart that may help. Industrial Sewing Machine has a similar cross-reference that might be easier to read. You probably aren’t making machine lace embroidery, but if you are, you may find Dotec’s small cross-reference handy.

*[footnote] Readers who valiantly waded through my article on thread sizes may wonder how we relate needle diameters to thread sizes, when thread sizes obstinately refuse to provide actual thread diameters. The answer is painful. First we have to go from blade diameter to recommended thread diameter. The eye of a needle is smaller than the blade which contains it. Depending on needle system design, that might be 40% to 60% of the blade diameter, and half of the eye diameter is the ideal thread diameter. Once we have a target thread diameter, we have to convert to a thread size. This requires an estimate of the thread’s density or specific volume, and doing some algebra (convert diameter to cross-sectional area to weight to thread size). Then, if you are sensible, you will cross-check against various thread, needle and machine makers’ recommendations (which vary widely) for sanity.

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  1. mack says:

    I was just reading the thread sizing post and it reminded of another mysterious numbering system;the system used to donate needle sizes.

    In my studio we have a ragtag gang of old industrial straight stitchers , some very old (no back tack function!!) and some just plain old. They are all in great working order, very reliable and each has its own personality and fabric likes and dislikes. Each also uses a different size needle, which is very annoying but not that surprising as they are from totaly different eras. A couple must be from the 40s ,one looks like it may be 50s and another from the early 80s they are all Singers.

    Each time we run out of needles for one of the machines we have to take the little plastic needle holder I tape to each machine to the store as a reference to get more. After all these years ( I have been with them for 4 years) I am still dumbfounded at the codes and numbers used to reference needles. They obviously state the thickness of the needle which is for use on different weight fabrics but what else.
    For example one label it states :

    DP x 5
    135 x5

    Another :

    UR x 128GAS
    036/14 SES

    My personal favourite:

    1738 SY2254
    16 x 95 SY2270
    16 x 231 DB x 1
    16 x 257 DB x 257
    90/14 SUK/BP

    What are all these numbers?

    Some clever sewer has actually scratched 135 x 7 into the paint job of one machines which has proved helpful for figuring out which needle that one takes.

    Am I missing something? Did I miss that class in school (probably not, they generally miss out the useful stuff). Is this just another industry oddity that everyone just accepts?

    Is there any way to know what size needle a machine takes without a instructional booklet (long lost), or talking to a mechanic?

  2. sfriedberg says:

    Mack, your question is well-timed! Part three will cover that cryptic stuff in (too much) detail. The short answer for your three examples is that the last line is the needle size (e.g., 90/14) and the point/tip type (e.g., SUK/BP). All the other lines are various names for the needle system. All the names in each example are equivalent, like aliases in a bad spy movie.

    “Dumbfounded” is a perfectly reasonable reaction! The naming schemes are absolute chaos.

  3. sfriedberg says:

    Mack, I took a closer look, and you have a lurker here hiding in your examples.

    The 036 in “036/14” is a Union Special size, which I had not mentioned since that system is rarely used. Fortunately the “14” part gives the Singer size, and the size cross-reference charts linked in the article let us confirm that 036 Union Special does indeed match up with 14 Singer.

  4. Connaye says:

    I just bought a singer 29k70. I have downloaded a manual but I am finding that the upolstry thread I am using may not be right for this machine. I am making a bike seat. I have read in the manual that “always use thread with corrsponding size of needle as per table ” What table? Where do I find a table that gives you this information?

  5. sfriedberg says:

    Connaye, there’s a little link up above, in the text of the article, that gives you a table for what Tex thread sizes go with which needle sizes. If Tex thread sizes aren’t familiar, you can read this article to relate Tex to more familiar thread sizing systems.

  6. diana says:

    Quick question. I have a consew 230 sewing machine. I want to sew leather bridles and make chaps. The machine states that I need to use needle size 16 x 257. Will that be a strong enough needle. I don’t understand the sizing well enough to know. What is the neaviest needle that I can use in that machine??? Thank you for your help.

  7. sfriedberg says:

    Diana, this reply is probably too late to do you any good, but the “16×257” is a needle system, not a size. You can get needles in that system easily up to size 18/110 and up to 24/180 with a bit of hunting (try

    As to the largest needle you can use in that machine, Consew’s manual for the 230 would be the right place to look. (Sorry, I don’t have one.) Because that model is intended for heavy work, I would presume that you can use any medium-to-large 16×257 needle and that it would have more problems with a small needle than a large one. You might have to adjust the hook timing slightly for best results if you make a big change in needle size.

    As to whether that needle system would be strong enough, you don’t have much choice. That’s the way they built that machine. However, if you look hard enough (or get your sewing supplier to look hard enough), there are are few modifications of the 16×257 system with different shanks that might be tougher than the basic system. I am not enough of an experienced sewing mechanic to make a specific recomendation for a different needle system; please consult your mechanic or supplier. I would recommend buying a premium brand of needles rather than a bargain brand for this kind of work. Since you can buy 100 industrial needles for $15 to $25, buying quality should not be an obstacle!

  8. sfriedberg says:

    I need to add a caution to the 2nd paragraph in the comment I just wrote. The 16×257 system (also known as DBx1, among other aliases) is unusual in that the larger needle sizes, specifically those larger than 18/110, have larger butt diameters. That means that size 19 and up needles in that system might not fit in a machine designed for that system. Because the Consew 230 is a very heavy work machine, it probably has been built to accept the larger sizes, but I can’t tell you that for sure. If you don’t have the manual, you can call Consew (212-741-7788) and ask them.

  9. kloeckner says:

    je recherche des aiguilles (si possible 10) pour surjeteuse “union special 81200C”
    pour la dimension 300/29. J’ai du mal à naviguer sur votre site à cause de la langue.
    Je peux vous payer par carte visa, mais c’est très urgent.

    Merci de me répondre en urgence.


  10. Kathleen says:

    I tell you, somebody should develop an app for this. Problem is, it would take time to compile and code but nobody (users) would want to pay for it. Ideally, all the machine and needle people would cooperate to be inclusive of competing needle systems but it probably won’t happen.

  11. Jackie says:

    Could someone help me please.
    I have a industrial singer sewing machine and having trouble finding needles to fit, the last lot of needles i bought fitted in the shank, but the blade was too long and kept on hitting the bobbin, could someone tell me the size of a needle with a shorter blade with the same shank size. The size on the box which i have bought is DBx1 100/16.

    • Spencer says:

      Jackie, I believe you need to adjust your needle bar. The shaft that moves the needle clamp up and down. If you’re not comfortable doing this, bring it to your local sewing tech.

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