Thread Weight Converter
Convert sewing, quilting, embroidery, and serger thread between wt, Tex, Denier, and metric Nm. Use it to compare labels, choose a similar thread, and understand whether a thread is fine, everyday, or heavy.
Convert a thread size
Enter the thread label you have. The result updates immediately with equivalent sizes and practical sewing guidance.
40 wt thread is approximately Tex 25, Denier 225, and Nm 40. It is a common everyday size for quilting cotton and general machine sewing.
How thread sizes compare
- wt: higher numbers are usually finer. 60 wt is thinner than 40 wt.
- Tex: higher numbers are thicker. Tex 70 is heavier than Tex 30.
- Denier: higher numbers are thicker. Denier equals Tex × 9.
- Nm: metric count. Higher numbers are finer, similar in direction to wt.
Thread brands do not always label wt the exact same way, especially for cotton versus polyester. Use this converter as a close comparison, then test stitch tension on a scrap before sewing the final project.
Common thread conversion chart
| Thread label | Approx. Tex | Common use |
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Thread weight conversion FAQ
What does 40 wt thread mean?
40 wt is a medium thread weight often used for quilting, machine embroidery, and general sewing. In practical conversion terms, it is roughly Tex 25 and Denier 225.
Is Tex 30 close to 40 wt?
Tex 30 is slightly heavier than the simple 40 wt estimate of Tex 25. It can still be in the everyday sewing range, but check the brand label and test your needle and tension.
What needle should I use with converted thread sizes?
Fine 60 wt thread often works with smaller needles around 65/9 to 75/11. Everyday 40–50 wt thread often works with 75/11 or 80/12. Heavier Tex 60–70 thread may need 100/16, 110/18, or a topstitch needle.