Yarn Weight Converter
Convert yarn weight between tex, denier, wraps per inch (WPI), and categories from lace to super bulky.
Includes recommended needle and hook sizes.
Type in any field — the others update instantly.
Yarn weight describes the thickness (linear density) of yarn.
Key relationships:
- Tex = grams per 1,000 meters of yarn
- Denier = grams per 9,000 meters of yarn
- 1 tex = 9 denier (exact)
- 1 denier = 0.1111 tex
WPI (Wraps Per Inch): WPI measures how many times yarn wraps around a ruler per inch. Thicker yarn = fewer wraps. Thinner yarn = more wraps.
Standard yarn weight categories (approximate):
| Category | Tex | Denier | WPI |
|---|---|---|---|
| Lace (0) | 25–50 | 225–450 | 30–40 |
| Fingering (1) | 50–100 | 450–900 | 19–22 |
| Sport (2) | 100–150 | 900–1,350 | 15–18 |
| DK (3) | 150–200 | 1,350–1,800 | 12–14 |
| Worsted (4) | 200–300 | 1,800–2,700 | 9–11 |
| Bulky (5) | 300–450 | 2,700–4,050 | 7–8 |
| Super Bulky (6) | 450+ | 4,050+ | 5–6 |
WPI is an approximation since it depends on fiber type and twist.
Tex and denier both measure linear density, the weight of a fixed length of yarn, just on different reference lengths. Denier (grams per 9,000 m) comes from the silk trade and survives in synthetics, which is why pantyhose are sold as “20 denier” or “70 denier,” the higher number being thicker and more opaque. Tex (grams per 1,000 m) is the cleaner, more modern unit, and the two convert simply since one tex is nine denier.
WPI, or wraps per inch, is the hand-knitter’s practical trick: wind the yarn around a ruler and count the wraps in an inch. It needs no scale and works with a ball that’s lost its label, which is why crafters rely on it. The catch is that the standard weight categories (lace, fingering, DK, worsted, bulky) overlap at the edges and depend on fiber and twist, so two “worsted” yarns can knit up noticeably differently. Always check gauge with a swatch rather than trusting the category alone.
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This converter runs entirely in your browser, so the numbers you enter stay on your device. The math behind it is written by hand and tested against worked examples and standard references before the page goes live.
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