Thread Weight Comparison Calculator
Compare two threads by weight (wt), tex, denier, relative thickness and price per 100 metres, then see how many spools your project needs.
Which Thread Is Thicker And Better Value?
Enter the weight rating, spool length and price for two threads, plus how much thread your project needs. The calculator converts to tex and denier and compares cost and thickness.
Thread Weight Comparison Estimator
Thread weight (wt) equals kilometres of thread per kilogram, so higher wt means thinner thread.
Understanding Thread Weight
Key concepts for thread choice
Weight (wt)
The weight number equals kilometres of thread per kilogram. 40 wt means 40 km weighs 1 kg.
Tex And Denier
Tex = 1000 ÷ wt (grams per km). Denier = tex × 9 (grams per 9 km).
Relative Thickness
Diameter varies roughly with the square root of tex, so a 40 wt thread is about 1.12x the diameter of a 50 wt thread.
Cost Per 100m
Price ÷ length × 100 is the fairest cost comparison between spools.
Common Thread Weights
Approximate tex values and typical uses.
| Thread Weight | Approx. Tex | Thickness | Typical Use |
|---|---|---|---|
| 12 wt | 83 | Very thick | Decorative stitching |
| 28 wt | 36 | Thick | Quilting, topstitching |
| 40 wt | 25 | Medium | General sewing, quilting |
| 50 wt | 20 | Fine | Piecing, machine embroidery |
| 60 wt | 17 | Very fine | Applique, detail work |
| Rule of Thumb | Higher wt = finer | Match to needle size | Test on scrap |
Thread Weight Calculator FAQ
Answers to common questions about this calculator.
Weight (wt) is the number of kilometres of thread needed to weigh one kilogram, so a higher number means a finer thread.
40 wt and 50 wt are popular for piecing and quilting, while 12 to 28 wt suit decorative stitching.
No. Ply describes how many strands are twisted together, while weight measures overall thickness.
Yes, generally. Match needle size to thread so it moves smoothly without shredding.