Sewing Thread Size Numbering System

Sewing thread size:
Sewing thread is a very important element for making complete garment. Threads are usually made up of several single strands twisted or plied together. Sewing thread size or count is a numerical expression used to indicate threads size, is the relationship between length and weight of yarn. Threads come in a bewildering array of types and sizes. To make matters worse there are several non-compatible thread size systems and each supplier seems to use a different system.

Sewing Thread Size

Before sewing machines there were only a few sizes of thread. As sewing machines and weaving machines were developed for specialized purposes, thread was developed for these machines in numerous sizes and types. This development happened separately in many countries around the world and consequently many different thread size systems were developed.

Most threads sold for home use are not labeled with a thread size. You have to search on the suppliers web site for the thread size information and possibly download a specification sheet. Most thread sold for industrial use is sized using the size system preferred by the thread manufacturer and labeled accordingly. In most thread size systems the size of the thread is defined by a calculation that takes into account the length and weight of a specified amount of thread, not by measurement of the diameter of the thread as you might expect.

To measure the thread size using these systems you must take a known length of thread, weigh it with a very accurate scale and then do some mathematical equations. The type of scales needed to do this are expensive.

It would be nice if there was a simple and inexpensive thread size meter, but there is no such thing. On a practical level however you can use a device called a micrometer to do a good approximate measurement of thread size.

Standardizing and converting:
With the many conflicting thread size systems in use you may want to standardize on the Tex system and convert all of your thread size information to that system. You can use a micrometer to measure the approximate Tex size.

You can also try to use equations or conversion charts to convert the thread sizes from one system to another, but you may find that this turns into an exercise in frustration. This is because there are many different aspects of thread measurement systems that can be miss-stated or miss-understood.

For example;

  • Many systems only measure one strand of the twisted thread and then use a strand multiplier (such as 120/3). It is often not clear if the thread size is reflecting the overall thread size or just one strand.
  • The stated thread sizes are many times different than the actual measured thread size! This is due to a variety of factors such as if the specification is for the thread before dyeing (coloring) or after.
  • Another discrepancy can come from what is known as bracketing. Bracketing is the practice of rounding the actual thread size up or down to the closest standard size.

If you want to be accurate and save yourself from frustration then measure the thread yourself.

The Tex system:
The Tex system is the most widely used thread size measurement system and is used worldwide. It is the ISO standard (International Organization for Standardization).

Most thread suppliers will list the Tex sizes for their threads or have a conversion chart available so that you can convert their thread sizes to Tex.

The Tex system is intuitive because the numbers increase as the thread sizes get larger. Some other systems have smaller numbers for larger thread sizes or the numbers are arbitrary and this is confusing.

The Tex size is determined by the weight (in grams) for 1000 meters of thread. The Tex system is called a fixed length system because a fixed length of thread (1000 meters) is weighed to determine the thread size.

The Tex system is bracketed, this means that the sizes are in discrete steps and the actual sizes are rounded down to the closest step size. For example if the actual thread measurement is 67 the thread size would be rounded down to the closest Tex size which is T-60.

The common Tex sizes in the bracketed series are 10, 12, 16, 18, 21, 24, 27, 34, 40, 50, 60, 70, 80, 90, 105, 120, 135, 150, 180, 210, 240, 270, 300, 350, 400, 500, 600, 700

Not all thread manufactures bracket the thread sizes, this explains why you will sometimes see strange sizes that are not in the series.

Tex size will appear as T-nn (such as T-40 or T-105 or whatever the size is) (nn means number).

Most thread is composed of multiple strands. The Tex measurement is for the entire thread and not the individual strands.

Other size systems:
Denier: Denier (d) is another fixed length system similar to Tex except that the Denier size is the weight in grams for 9000 meters of sewing thread. The Denier size is 9 times the Tex Size. Denier sizes will appear as nnd (such as 55d or 70d or whatever the size is). To convert from Denier to Tex the equation is den/9 = Tex

Commercial Size: The Commercial Size system is for threads used in upholstery, technical sewing (camping gear, tents, backpacks), webbing and straps for trucks and boats, sails, etc. Common sizes are 15, 23, 33, 46, 69, 92, 138, 207, 277, 346, 415 and 554. The Commercial Size system is based on the Denier system divided by 10. To convert from Commercial Size to Tex the equation is (Size*10)/9 = Tex. For example Commercial Size 69 converted to Tex (69*10)/9 = 76 and in Tex we round that down to the nearest step size of T70

Metric Counting (Nm): Nm stands for "Number Metric". Nm is the number of meters of a strand that weighs one gram followed by the number of strands that make up the thread. For example Nm 120/1 is composed of one strand of thread and one gram of that strand is 120 meters long. 50/3 is composed of three strands of thread and one gram of a single strand is 50 meters long. The Metric Counting system has mostly been replaced by Label Number (No).

Label Number (No) or (Tkt): This system is similar to the Metric Counting (Nm) system, but it does not specify the number of strands. It is assumed to be talking about the entire thread regardless of the number of strands. The lower the number, the thicker the thread. For example No 100 would describe a thread in which one gram is 100 meters long. The Label Number system has largely replaced the Metric Counting system with most manufacturers. Gutermann uses the Label Number (No) system. To convert from Label Number to Tex the equation is 1000/No * 3 = Tex. In case you are wondering where the “* 3” came from in the equation, the Label Number (No) is based on the cross-section of a three strand thread, even when there are actually a different number of strands. You may have noticed that Tkt is also used to stand for “Ticket” as in the arbitrary Ticket (Tkt) system – yes this is confusing! That is why it is a good idea to measure the thread your self to be sure.

Weight (WT): This system is known as “Thread Weight” and is the number of meters of a thread that weighs one gram. This system is the same as the “Label Number” system above. To convert from Weight to Tex the equation is 1000/Wt * 3 = Tex

Cotton Count (Nec), (Ne) or (cc): Used for all types of spun threads including polyester thread. The name Cotton Count originated before polyester came into use. Cotton Count is the number of strands that are 840 yards long that it takes to equal 1 pound. A Cotton Count of 20 means that 20 strands of thread 840 yards long weigh 1 pound. To convert from Cotton Count to Tex the equation is 590.54/NeC * Strands = Tex. In this case “Strands” equals the number of strands in the thread, for example if you wanted to convert a Nec 50/3 to Tex the equation would be 590/50 * 3 = 35.4 and we just round that down and call it Tex 35

The Hong Kong Ticket system - is the same as the cotton count system, but is written without the notation and the slash. An Nec 50/3 thread would be a 503 in the Hong Kong Ticket system.

Ticket (Tkt): There are many manufactures that still use arbitrary “Ticket” numbers. These ticket numbers are product identification numbers and may or may not have any relationship to the actual size of the thread.

Thread Size (#): This is a semi-arbitrary system used by many manufacturers of embroidery thread and is also popular with Asian manufactures of spun polyester thread. Thread Size numbers are based on fine, medium, and heavy categories. Fine threads are about #70, Medium threads are about #50 and Heavy threads are about #20. Common sizes and the approximate Tex equivalent are; #6=T190, #10=T140, #16=T105, #20=T70, #30=T60, #40=T50, #50=T40, #70=T27, #100=T24.

US Gov. A-A-59826 Type III(VT295E): This is one of several US government systems that are number and letter based. Another one is called US Gov. A-A-59826Type I & II. These systems are primarily used in US government contracts. You may be able to download the specifications for these systems using the Internet. They are mentioned here so that if you come across them you will know what they are. Some typical thread sizes (Multifilament Nylon Thread) in VT295E and the Tex equivalents are as follows; OO = T16, A = T24, AA = T30, B = T45, E = T70, F = T90, FF = T135, #3 = T210, #4 = T240, #5 = T350, #6 = T450, #7 = T500, #8 = T600, #9 = T700


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Mazharul Islam Kiron is a textile consultant, entrepreneur, blogger and researcher on online business promotion. He is working as a consultant in several local and international companies. He is also a contributor of Wikipedia.

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