How to use this calculator
- Enter or choose picks per inch (PPI).
- Enter or choose reed width.
- Enter or choose fabric length.
- Enter or choose wastage.
- Enter or choose weft count.
- The weft yarn needed updates as you type. Use Copy result or Share to keep it.
Method
Picks = PPI × 39.37 × Length (m); Weft kg = Picks × Reed width (m) × (1 + Wastage%) × Tex ÷ 1,000,000
- PPI
- picks per inch in the fabric
- Reed width
- width of the warp in the reed (1 in = 0.0254 m)
- Tex
- grams per 1000 m (Ne converts as 590.54 ÷ Ne)
Worked example
- Picks = 80 per inch ÷ 0.0254 m × 1,000 m = 3,149,606.
- Each pick is 63 in = 1.6002 m long, so weft length = 3,149,606 × 1.6002 × 1.03 = 5,191,200 m.
- Ne 30 = 590.54 ÷ 30 = 19.685 tex, so weight = 5,191,200 × 19.685 ÷ 1,000,000 = 102.19 kg.
1,000 m of fabric at 80 PPI on a 63-inch reed in Ne 30 weft needs about 102.2 kg of weft including 3% wastage.
What the result means
Add warp and weft weights for the total yarn order; their sum divided by fabric area is a good cross-check against the fabric GSM.
Assumptions and limits
- Weft crimp is covered by using the reed width rather than the fabric width.
- Wastage is a percentage of the weft length.
- Shuttleless looms with tucked-in or leno selvedges add a little extra weft per pick that is not modelled separately.
Questions
Why use reed width instead of fabric width?
The weft is inserted across the reed and then the fabric narrows as the weft crimps, so reed width already includes weft crimp.
Can I use denier for the weft?
Yes. Choose denier as the count system; it is converted to tex as denier ÷ 9.