Thread-to-needle size calculator.
Use a printed Tex number to find a supplier’s suggested needle-size range, then compare it with the manufacturer’s size list for a material family. The overlap is a test candidate—not a guaranteed size or machine-fit result.
United Kingdom edition. This calculator uses a supplier chart and manufacturer family ranges, not a UK-market conversion. Treat any overlap as tentative and verify the exact thread and machine documentation. UK terminology and label notes.
Build a cautious starting range
Supplier chart + manufacturer family data.
Starting-point calculator
Enter a documented Tex value, choose a material family, and compare the ranges.
How the comparison works.
The calculator reads the WAWAK Tex-to-machine-needle chart and the size list for the selected SCHMETZ household needle family. It then shows the metric sizes present in both lists. If the chart range is between two entries, it preserves both as a supplier range.
It does not transform thread weight systems, infer an unprinted Tex value, estimate machine capacity, or validate stitch quality. The machine maker’s manual and a scrap test remain part of the process.
Questions and risk labels.
Why can the calculator give a size range but not one answer?
The thread chart is a general starting reference. Needle-family size depends on material, thread behavior, machine constraints, point, needle eye, and the selected system. The overlap is a comparison to investigate, not a certainty score.
What if the ranges do not overlap?
Do not force a match by upsizing or changing systems. Confirm thread data, material family, needle family, and the manual. Some thread/needle combinations may be outside this chart or outside the machine’s capacity.
Can I enter 40 wt instead of Tex?
No. Different thread standards use different numbering direction and conversion rules. WAWAK’s conversion chart shows that Tex, weight, denier, and ticket systems have specific formulas and limits. This calculator accepts only a labelled numeric Tex value.
Evidence behind the calculator.
- WAWAK Tex-to-Machine-Needle Size Chart — supplier range (opened October 19, 2026).
- WAWAK Machine Needle Selection Guide — distinguishes system, size, and point type.
- SCHMETZ Topstitch family
- SCHMETZ size-pair table
Research basis includes a Reddit request for a fabric/thread/needle guide (r/sewing, May 20, 2024) and a DBx1 thread-size question (r/sewing, February 3, 2025). Community posts describe the pain; WAWAK supplies the chart; SCHMETZ supplies material-family ranges. Source tiers remain distinct.