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Thread Weight Converter – Online Tex, Denier, Wt, Nm

Converter Crafts & DIY converter thread weight
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Thread Weight Converter

Instantly convert between Tex, Denier, Wt (Weight), and Nm (Metric Count)

Tex
grams per 1000 meters
Tex
Denier
grams per 9000 meters
Den
Weight (Wt) approx.
sewing thread weight
Wt
Nm (Metric Count)
meters per gram
Nm
Enter a value in any field to convert instantly
Common Sewing Thread Weight Reference
Wt (Weight) Tex (approx.) Denier (approx.) Nm (approx.) Typical Use
20 Wt 50.00 450 20 Heavy-duty, upholstery, leather
30 Wt 33.33 300 30 Jeans, heavy fabrics, topstitching
40 Wt 25.00 225 40 All-purpose sewing, quilting
50 Wt 20.00 180 50 Fine sewing, piecing, appliqué
60 Wt 16.67 150 60 Very fine detail, heirloom sewing
80 Wt 12.50 112.5 80 Micro quilting, fine embroidery
100 Wt 10.00 90 100 Invisible stitching, silk threads

Values are based on the approximation Wt ≈ Nm ≈ 1000/Tex. Actual thread specifications may vary slightly by brand and manufacturer.

Conversion Formulas
Tex = 1000 / Nm
Tex = Denier / 9
Tex ≈ 1000 / Wt
Denier = Tex × 9
Denier = 9000 / Nm
Denier ≈ 9000 / Wt
Wt ≈ 1000 / Tex
Wt ≈ 9000 / Denier
Wt ≈ Nm
Nm = 1000 / Tex
Nm = 9000 / Denier
Nm ≈ Wt
Frequently Asked Questions

Tex is a unit of linear mass density used in the textile industry. It measures the weight in grams of 1,000 meters of thread or yarn. A higher Tex number indicates a thicker, heavier thread. For example, Tex 25 means 1,000 meters of the thread weighs 25 grams. Tex is part of the International System of Units (SI) and is widely used in industrial textile applications worldwide.

Denier measures the weight in grams of 9,000 meters of thread or yarn. Since Denier uses a longer reference length (9,000m vs 1,000m for Tex), Denier values are always 9 times larger than Tex values for the same thread. Denier is commonly used for synthetic fibers like nylon and polyester, especially in the United States. Conversion: Denier = Tex × 9.

Wt (Weight) is a commercial grading system used primarily for sewing threads. It is an approximate value where Wt ≈ Nm ≈ 1000/Tex. In this system, a lower Wt number means a thicker thread (e.g., 30Wt is thicker than 50Wt). Common sewing thread weights include 30Wt for heavy fabrics, 40Wt for all-purpose sewing, 50Wt for fine work, and 60Wt+ for delicate applications. Note that Wt is an approximation and exact Tex/Denier equivalents can vary by brand.

Nm (Metric Count) indicates how many meters of thread weigh 1 gram. It is the inverse of Tex: Nm = 1000 / Tex. A higher Nm means a finer thread (more meters per gram). For example, Nm 40 means 40 meters of the thread weighs 1 gram, which corresponds to Tex 25. Nm is widely used in Europe and for cotton and wool yarns.

Using the standard approximation Wt ≈ 1000/Tex:
• 40Wt ≈ Tex 25.00 (1000 ÷ 40 = 25)
• 40Wt ≈ Denier 225 (25 × 9 = 225)
• 40Wt ≈ Nm 40
This is why 40Wt is considered an all-purpose sewing thread — it balances strength and finesse. Keep in mind that different manufacturers may have slightly different specifications, so always check the actual Tex or Denier on the spool for precision work.

For quilting, the most commonly recommended thread weights are:
• 50Wt (Tex ~20) — Ideal for piecing and detailed quilting. It creates fine, precise seams with less bulk.
• 40Wt (Tex ~25) — Great for general quilting and visible topstitching. Slightly thicker for more pronounced stitches.
• 60Wt (Tex ~17) — Excellent for micro quilting and intricate designs where you want the thread to blend in.
• 30Wt (Tex ~33) — Used for bold, decorative quilting where the thread is meant to stand out.

The Wt (Weight) system is a commercial convention, not a strict scientific measurement like Tex or Denier. Different thread manufacturers (such as Gütermann, Aurifil, Superior Threads, and Coats) may assign slightly different Wt numbers to threads with the same actual Tex value. For example, one brand's 50Wt might be Tex 20, while another's might be Tex 22. For precision applications, always refer to the Tex or Denier value printed on the spool, as these are based on actual measured weight per length.

Both Tex and Denier measure linear mass density, but they use different reference lengths:
• Tex = grams per 1,000 meters
• Denier = grams per 9,000 meters
This means Denier is always 9 times Tex for the same thread. Tex is more common in industrial and international contexts, while Denier is traditionally used for synthetic fibers in the US market. For sewing threads, Tex values typically range from about 10 (very fine) to 70 (very heavy), while Denier ranges from about 90 to 630.

This converter uses the standard mathematical relationships between Tex, Denier, and Nm, which are exact conversions:
• Tex ↔ Denier: exact (factor of 9)
• Tex ↔ Nm: exact (Nm = 1000/Tex)
• Wt conversions use the industry approximation Wt ≈ 1000/Tex ≈ Nm, which is accurate enough for most sewing and crafting purposes. For the most precise thread specifications, always consult the manufacturer's data sheet or spool label. The converter displays results to 2 decimal places for Tex and Nm, and 1 decimal place for Denier and Wt, which is sufficient for virtually all practical applications.
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