Thread Weight Guide for Beginners

This article will supply you with knowledge about thread weight, its types, and the different ways it can influence the outcome of your project.
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Last updatedLast updated: May 17, 2021

Perhaps the most important decision any sewer can make when embarking on a new project is selecting the right thread. After all, the thread is literally what holds everything together. Regardless of whether you are sewing by hand or with a machine, choosing the right thread is imperative to the overall success of your project. But how do you know which thread to choose? In addition to color and material, the other essential characteristic to consider when selecting your thread is thickness and thread weight.

What is a thread weight?

Thread Weight Guide for Beginners

There are five commonly used methods of measuring thread – weight, denier, tex, number system (also known as the Gunze Count System), and composition standard. Thread weight is a length measurement and is determined by measuring one gram of thread. For example, if the length of one gram of thread is 30 meters long, then that thread’s weight is 30. Thread weight should be considered at the start of every sewing project because of its impact on the outcome of the final product. But reading these numbers and determining which is right for you can be a confusing process. All threads have a weight to them, which refers to the thickness of the thread. The lower the thread weight, the thicker the thread actually is. This number is arbitrary and can vary from one manufacturer to the next. It is important to keep this in mind when selecting your project’s thread. For example, No. 50, #50, 50 wt, and 50/3 are not the same thing and are all measuring different aspects of the thread. Therefore, the best way to determine the right thread weight for your project is to run the thread through your fingers and actually feel its thickness.

Types of thread weight

Thread Weight Guide for Beginners

Thread weights are listed as numbers on the side or the bottom of the spool. The most common threads are considered all-purpose 50 weight threads. These are usually polyester threads or a cotton-polyester blended thread. These threads tend to be durable and will stitch your fabric together without much bunching or visible lumps. 40 weight threads are shiny embroidery threads and are best used with sewing machine work. These threads are typically made of rayon or polyester. Rayon isn’t considered as durable as polyester. 40 wt threads can also be used for adding decorative stitching to your garments. Lower thread weights, like 12-18 weight threads, are mostly used for specific sewing projects such as hand stitching or topstitching projects. Threads at this weight need to be higher in quality because the outcome of your project depends on their durability. For example, cutting corners on the quality of these threads can lead to fraying of your garment or breaking of the thread. Additionally, 30/40 threads make quilting stitching pop and are recommended to consider as alternatives to 100% cotton threads for these kinds of projects. Serger thread is a 40 wt polyester thread with a special coating that allows it to maintain the high speed and tension of serging. This thread tends to be a bit heavier than 50 wt thread, which may not make much of a difference depending on your project type.

Why is it important?

The weight system is used to determine the overall diameter of the thread. This key characteristic of the thread drives much of the rest of the sewing project. In fact, thread weight will influence a majority of the aspects of your project, such as stitch density, needle size, and density. Understanding this number is key to putting together the framework of your sewing project.

Keep in mind that heavier threads will create a more visible motif whereas lighter threads will create better texture and are more useful for background effects in quilting.

Additional Information

Sometimes the thread weight is listed as a fraction, for example, 60/2. The numerator (top number) refers to the weight of the thread, and the denominator (the bottom number) refers to the number of plies or strands twisted together on the spool. In the example 60/2, this number indicates a thinner thread (remember, the higher the number, the thinner the thread) that has two plies.

The least common thread weights are 28 wt and 60 wt bobbin thread. The 28 wt thread is used as an alternative for specialized handsitching and topstiching projects. The 60 wt bobbin thread is used for embroidery projects.

Lastly, some spools do not list the thread weight on the label. If that is the case, you will need to estimate the thread weight by touch. You can also go online to the manufacturer’s website to look up the actual thread weight.

Final thoughts

Remember that the higher the thread weight number, the thinner the thread. Knowing the thread weight number can also help you determine the other measurements of your thread as these characteristics are all intertwined. For example, dividing 9000 by your thread weight will give you your thread’s denier number, since denier is the weight of 9000 meters of thread. Similarly, dividing 1000 by your thread weight will reveal your thread’s tex, since tex measures 1000 meters of thread in grams.

The best way to choose the right thread weight for your project is through trial and error. Now that you have an understanding of the basics and if you keep in mind these important points, you can’t go wrong with your selection. It will become a matter of preference, and the best way to determine what is right for you is to give all thread types a try.

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