The Polyester Thread Buying Guide helps customers get the right thread for their needs. Our approach is to help you decide if polyester is the right thread for the job, identify which sizes (thicknesses) should be used, and finally pick the color and spool size that works. We have polyester thread in eleven sizes, over 100 colors, and putups ranging from small spools priced around $10 to discounted cases.
Polyester Thread Uses - Polyester thread looks, feels, and sews like nylon. You cannot tell the difference just by looking at the thread and differences in many technical specifications are insignificant. This means that polyester works just as nylon in most applications including: upholstery, leatherwork, auto interiors, banners and flags, sports gear, dog collars, horse saddles and tack, knife sheaths, gun holsters, fishing lures, and brief cases.
Polyester is a better choice when there is prolonged exposure to sunlight, mildew, bleaching, acids, or alkalis. These include: marine and outdoor upholstery; tarpaulins and pool covers; flags and banners left outside; and convertible tops especially in the Southwest. It is important to distinguish between prolonged and occasional. There are many things that are taken outside but not left outside such as tents, clothing, sports gear, and most leatherwork. In these cases nylon and polyester work equally well.
Polyester thread does not provided the ultimate sunlight (UV) resistance. Brands like Sunbrella and Tenara come with replacement guarantees and UV treated nylon and polyester threads will out perform regular polyester. None of this matters if the material sewn is not equally bleach and sunlight resistant. After all, the material makes up at least 90% of the content and cost of the item that is being sewn.
There are times when polyester thread should not be used:
Spun Polyester - Most garments are sewn with some type of spun polyester. This kind of thread is a thin strand of polyester thread wrapped in a cotton outer layer. It is very inexpensive and has a soft, cotton-like texture.
Fire retardant garments and gear- Polyester thread
sticks at 440Fto 445F and melts at 483Fahrenheit.First responder garments and gear and some high temperature conveyer belts require much more fire retardance.UseKevlar and Fire Retardantin these situations. All are heat resistant to 700F and does not melt.
Critical strength requirements- Polyester is strong but Kevlar Threadis about twice as strong. For example, size 92 polyester as a 14.5 pound tensile strength; the same size Kevlar has a 30 pound tensile strength. Kevlar's downside is that it costs about five times more than polyester and only available in yellow. Consider using heavier weight polyester or double-stitching to meet strength requirements.
Polyester Thread Size -
Thread size refers to the thread's approximate thickness. Thread is soft and spongy and its thickness cannot be accurately measured with calipers. The Commercial and Tex sizes on our site measure the weight of a fixed length of thread. For example, a 1,000 meters of Tex 70 weighs 70 grams. Having said this, the military includes thread thickness in their specifications and we include them in our
Polyester Thread Specifications.
Thread size is important because it affects so many things:
When thread size increases...
When thread size increases...
Sewing machine size
Sewing heat and friction
Yards per pound
The material that you are sewing costs far more than the thread. In most cases (parachutes excepted) it is better for the thread to break than to have the stitches pull through the fabric. This means that the weight of the fabric, in ounces per square yard, is the best way to determine thread size. Here are size recommendations for fabric and leather.
Fabric Ounces Per Yard
Thread Size Range
Leather Ounces Per Yard
Thread Size Range
2 to 6 Ounces
15 to 33
1 to 8 Ounces
46 to 207
6 to 8 Ounces
33 to 46
8 to 12 Ounces
138 to 277
8 to 10 Ounces
46 to 69
12 to 16 Ounces
207 to 346
10 to 12 Ounces
69 to 92
207 to 346
12 to 14 Ounces
92 to 207
There other things to consider. You may use a thinner thread because your machine cannot handle a heavier thread. Or, you may choose a thicker thread because you want stitches to stand out.
Bonded or soft? - Bonded means that a thread has a coating that reduces needle heat and fraying. It makes thread stiffer and about 5% thicker than soft thread that does not have a coating. The choice between bonded and soft depends on how the thread is going to be used and thread thickness. Here are our recommendations:
Machine sewing lightweight
thread sizes 15 to 46
Lightweight thread sizes generate little needle heat and are unlikely to fray. Bonded and soft thread work equally well.
Machine sewing thread sizes 69 and higher
Bonded thread is strongly recommended
It does not matter if you use bonded or soft thread.
Wrapping and gluing
Soft thread is preferred because bonded thread often repels glues and adhesives. You can soak a bonded thread in alcohol to remove the bonding.
Other non-sewing applications such as hanging and reinforcing
Finish does not matter in most cases. Bonded thread is better if it is going through a narrow tube.
Spool Sizes -
We sell most of our polyester thread in 2 Ounce, 4 Ounce, and 16 Ounce (1 Pound) spool sizes or putups. The smaller putups cost more per ounce than the larger ones. But, they are a better choice for one-time jobs, casual sewers, people who need a stash of many colors, and experimenters.
Polyester thread is sold by weight (ounces, pounds) - not yards. This is because the number of yards-per-pound decreases as thread thickness increases. Selling by weight means prices for a given size spool are about the same across most thread sizes..
Industry norms allow polyester thread spool weights to vary by plus/minus 10% from the stated nominal weight. This means that customers get slightly less or slightly more thread than the nominal weight shown on our site. The table on the right shows our nominal weights and the thread-weight range ( including the spool's weight ) for various sizes. When spools fall within these ranges we do not charge for overages or refund underages. Here are the weight ranges we use:
Spool base width and height vary with the putup:
2 and 4 Oz
12 and 16 Oz
Polyester thread stretches about 25% before it breaks. This means that 10 yards of nylon thread will be 12.5 yards when it snaps. This stretchiness is a good thing in most cases. It allows the seams to expand and contract with the material and avoids puckering and breakage. Polyester's stretchiness may not be desirable in some hanging, reinforcing, or wrapping applications. When this is so, consider less stretchy threads such as cotton, spun polyester, or Kevlar.
Twist - Most of the polyester thread on our site
is left twist (also called Z-twist) because that is what single-needle machines made for the U.S. use. We have a few, clearly marked, right twist (also called S-twist) thread for double-needle machines. A thread's twist makes no difference when it comes to hand-sewing and non-sewing applications.
Inches - decimal
Inches - thousandths
2 Ounce Spool
4 Ounce Spool
8 Ounce Spool
12 Ounce Spool
16 Ounce Spool
Thread Size and Machine Type - As thread size increases, a more powerful machine is needed to push the thread through the material.
Thread Size /
Stitch Visibility -
Do you want the stitches noticed?
Polyester Thread Uses / Size Ranges -
Best size depends on material thickness, seam strength, stitch visibility and sewing machine size.