Synetic College Logo
Unit 2 of 4 · B.Sc Textile Sem 4

Unit 2: Warp/weft weight & cover factor calculations

Fabric Quality Analysis notes · PTU syllabus (BSTD 401-20)

3 min read4 topics9 exam questions
On this page
  1. Unit summary
  2. Warp weight calculation
  3. Weft weight calculation
  4. Reed width and tape length
  5. Cover factor
  6. Key terms
  7. Quick revision
  8. Important questions

Unit summary

Planning a fabric order means calculating how much warp and weft yarn is needed and how densely the fabric is covered. This unit covers warp and weft weight for a required length and width, reed width and tape length, and warp and weft cover factor.

After this unit you can

  • Calculate warp and weft weight for an order
  • Calculate reed width and tape length
  • Define and calculate cover factor
  • Relate cover factor to fabric properties

PTU syllabus topics

  • Warp and weft weight calculation to produce required fabric length and width
  • calculating reed width and tape length
  • wrap/weft cover factor definition and calculation
Key formulasWarp, weft and cover factor

  • Warp weight (g)

    (Total ends × warp length in m × (1 + crimp)) / (Ne × 1.693)

    A count of 1 Ne = 1.693 m per gram

  • Cover factor (Ne)

    EPI / √Ne

  • Cloth cover factor

    K1 + K2 − (K1 × K2 / 28)

  • Reed width

    Fabric width × (1 + weft crimp)

1

Topic 1

Warp weight calculation

Key formulasWarp weight

  • Total ends

    EPI × fabric width (inches) + extra selvedge ends

  • Warp length

    Fabric length × (1 + crimp %) plus wastage

  • Warp weight (kg)

    Total ends × warp length (m) ÷ (Ne × 1,693)

  • Alternatively

    Ends × length (m) × tex ÷ 1,000,000 kg

Example

1,000 m of fabric, 58-inch width, 132 EPI, 40s warp, 8% crimp: ends = 7,656; warp length = 1,080 m; weight = 7,656 × 1,080 ÷ (40 × 1,693) ≈ 122 kg (before wastage).

2

Topic 2

Weft weight calculation

Key formulasWeft weight

  • Weft length

    PPI × reed width (inches) × fabric length converted to inches (or picks per metre × reed width in metres × fabric length)

  • Weft weight (kg)

    Total weft length (m) ÷ (Ne × 1,693)

Example

Same order with 72 PPI, 40s weft and reed width 62 inches (1.575 m): picks per metre = 72 × 39.37 ≈ 2,835; weft length for 1,000 m of fabric = 2,835 × 1.575 × 1,000 ≈ 44.65 lakh m; weight = 44,65,000 ÷ (40 × 1,693) ≈ 66 kg, plus 2–3% wastage.

3

Topic 3

Reed width and tape length

  • Reed width: the width of warp in the reed, wider than finished fabric because weft crimp and shrinkage narrow it. Reed width = fabric width × (1 + weft crimp % + shrinkage allowance).
  • Reed count (Stockport): number of dents per 2 inches; ends per dent typically 2. Reed count = EPI × 2 ÷ ends per dent.
  • Tape length: length of warp on the beam = required fabric length × (1 + warp crimp %) + loom wastage (knotting, gaiting, cut-off).
4

Topic 4

Cover factor

  • Cover factor expresses the fraction of the fabric area covered by yarns — higher values give denser, more opaque, windproof fabrics.
Key formulasCover factor

  • Warp cover factor (K1)

    EPI ÷ square root of warp Ne

  • Weft cover factor (K2)

    PPI ÷ square root of weft Ne

  • Fabric cover factor

    K1 + K2 − (K1 × K2 ÷ 28)

  • Maximum value

    About 28 (fully covered) in this system

Example

132 × 72 with 40s × 40s: K1 = 132 ÷ 6.32 = 20.9; K2 = 72 ÷ 6.32 = 11.4; fabric cover = 20.9 + 11.4 − (20.9 × 11.4 ÷ 28) = 23.8.

  • Uses: comparing fabrics of different counts and densities, designing poplin vs sheeting, controlling air permeability.

Key terms

Reed width
Width of warp in the reed
Reed count
Dents per unit width of the reed
Tape length
Length of warp needed on the beam
Cover factor
Measure of how fully yarns cover fabric area
Wastage
Extra yarn lost in processing

Quick revision

  • Total ends; warp length with crimp; warp weight formula.
  • Weft length from picks and reed width; weft weight.
  • Reed width; reed count; ends per dent; tape length.
  • K1, K2, fabric cover factor; uses.

Important exam questions

Practice questions written to the PTU exam pattern for this unit's syllabus: short answers (Section A style) and long answers (Sections B and C style).

Short-answer questions

  1. Q1.Why is warp length longer than fabric length?
  2. Q2.Why is reed width wider than fabric width?
  3. Q3.What is reed count?
  4. Q4.Define cover factor.
  5. Q5.Calculate K1 for 100 EPI and 25s warp.
  6. Q6.What does a higher cover factor mean?

Long-answer questions

  1. Q1.Explain warp and weft weight calculations for a fabric order.
  2. Q2.Explain reed width, reed count and tape length.
  3. Q3.Explain cover factor with calculations.

Stuck on this unit?

Message SBS on WhatsApp for help with Fabric Quality Analysis, or to ask about studying B.Sc Textile at Synetic.

WhatsApp us