I was at Joann fabric store recently and couldn't figure out the thickness of the fabric or thread I was looking at. The fabric was just wrapped around some cardboard that just had a name and material. None of them had a denier (or anything else that I could identify as a thickness). The spools of thread were the same way.

I've attached a photo of what the spools generally looked like.

How am I supposed to find the thickness of the products I'm looking at? It seems like there should be a precise way of doing so, but I don't know what it is.

spool of thread without denier

  • 2
    Perhaps it would help if you explained why you want that information?
    – Catija
    Nov 6, 2017 at 14:59
  • because i like to be precise when building things and know exactly what i used so i can replicate it over time and across brands, colors, etc.
    – tau
    Nov 6, 2017 at 18:13

3 Answers 3


Textiles (in this case, thread and fabric), are highly engineered, complex structures around which entirely separate industries are built. For example, very few fabric manufacturers also make their own thread (which is technically a yarn). There are manufacturing specifications for every stage of textile manufacturer, from fiber to yarn to fabric to dyeing and finishing.

This means that the textiles we buy in fabric stores possess a set of layered specifications. For the average user, there may be one measurement at point of purchase, e.g., thread size or weight or fabric thickness, but that does not tell the whole story. Other combinations of these same variables can result in the same final number.

Thread size/weight can look pretty complex but it’s not as big of a mystery as it seems at first since fabric stores only carry a few sizes and weights and they are usually nicely labeled, e.g., all-purpose (or dual-duty or general use), quilting and embroidery, buttonhole, topstitching, etc. Granted, these are approximate weight classes, not exact specifications.

If you are a home sewer or crafter, select the fiber content you want, e.g., 100% cotton, 100% Polyester, core-wrapped (polyester wrapped in cotton), rayon, silk, etc. If you are quilting you will use 100% cotton, if you are sewing polyester knits, wovens or fleece you’ll want to use 100% polyester. As best you can, match the thread fiber content to the fabric fiber content, or use one of the dual-duty or general use threads.

One example of an explanation of thread weights and sizes: https://www.seasonedhomemaker.com/all-about-thread-weight/

Fabric weight and thickness also is composed of many variables. Fiber content, yarn size, fabric construction, etc. Every fabric has a different combination of these variables, but there are some fairly standard types. Fabric stores try to make it easy and stock quilting cottons together, fleece together, lining fabric together, etc. But, again, these will be approximate weight classes, not exact specifications.

One example of an explanation of fabric weights: http://blog.fabricuk.com/understanding-fabric-weight/

Unless you source your material (thread and fabric) directly from the manufacturer and obtain a spec sheet for each, you will still not be 100% sure of the thread or fabric specs.

If you are totally committed to knowing the manufacturing specs of your thread and fabric, you will need to contact the manufacturer of the thread or fabric, give them the UPC code on the end of the bolt (that’s that piece of cardboard you mentioned) or the thread label. It will not be possible for the average person to do their own testing, special equipment and expertise is required to do this sort of “fabric forensics.”

An alternative (which will be expensive) is to have a certified lab do your spec testing for you, e.g., http://www.gaston.edu/textile-technology-center/product-testing/physical-testing/

My practical recommendation is that you identify the exact thread (manufacturer, fiber content, use) and fabric (manufacturer, etc.) you want to use over time and build up an inventory. In other words, buy multiple spools of the thread, and multiple yards of the fabric off of the same bolt. At least this way you will know that your products are composed of the same weights and types.

Good luck with your projects, I applaud your interest in quality control. But, as they say, “Don’t let the perfect be the enemy of the good.” In this context, that may mean using the fabric stores’ descriptions of the thread categories and fabrics you use, or buy up a consistent inventory, but remember to have fun and enjoy the process.


While a caliper would be a great tool for calculating something like this most people do not have access to one. Coupled with the fact that the level of precision it provides is lost in most crafting endevours. There are some simpler techniques that you can use to get similar results.

For Fabric

Ever tried to measure the thickness of paper? Perhaps in school. Its near impossible as most rulers don't match that level of precision. What if you stacked multiple pages together? Putting 10 (or 20 or whatever) sheets together and you can easily measure the total and divide by quantity used.

For fabric reems this can get harder but you should still be able to fold it over itself several times without cutting it or anything. You could even roll it up and measure the outer layers. Either technique you use get you a decent figure to work with.

For Thread

When it comes to thread thickness I would like to borrow from another answer in this stack. Wrapping the thread around a ruler enough times to get a nice round number like a mm,cm or inch makes the math easier. Can you fit 10 rounds of thread in a mm? Then your thread is 1/10ths of a mm. Keep wrapping until the math is simpler.



To get the precise thickness of any object, you need a tool called a caliper. enter image description here

I'm not sure if that will help with the thread since that stuff is usually tightly bound and even plastic wrapped. But for fabric, it should work fine.

  • you are correct that calipers should measure thickness, but fabric/thread thickness is often specified in units (like deniers) that are all basically just measuring weight for a given length of thread, in which id need a tape measure and accurate scale. anyway, i would expect it is listed on the packaging, but i feel like i must be missing something...
    – tau
    Nov 6, 2017 at 6:08
  • 1
    Thank you! I didn't know that. ...and a quick search around the internet confirmed your statement that weight information about specific threads is not easy to find. I hope one of the other members can provide more help for your question. Nov 6, 2017 at 12:24

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