Professional calculators and comprehensive guides for corrugated box manufacturing, BOPP tape, paper tubes, timber, and packaging solutions. Expert tools for GSM calculation, box costing, flute specifications, and business insights tailored for packaging industry owners, engineers, and entrepreneurs in India.
Calculate estimated weight and total length of a paper reel using GSM, reel dimensions, core specifications, and bulk factor. Designed for paper mills, converters, corrugated box plants, and printing industries.
⚖️ Enter Reel Parameters
Grams per square metre of paper
Actual cut width of the reel
Full diameter of finished reel
Standard 3-inch core = 76 mm
Cardboard core wall thickness
Typically 1.3–2.0 for kraft/duplex
⚠ Please fill in all fields with valid numeric values.
📊 Calculation Results
Core Outside Diameter—
Paper Thickness—
Approximate Reel Length—
Approximate Paper Weight—
๐ Formula Used
Step-by-Step Calculation
1
Core OD (mm) = Core ID + (2 × Core Wall Thickness)
Bulk factor varies by paper type. Use as reference — verify exact value with your paper supplier.
Paper Type
Typical GSM
Bulk Factor (cc/g)
Kraft Liner (Brown)
100–200 GSM
1.10 – 1.30
Test Liner / Semi-Chem
100–180 GSM
1.20 – 1.45
Fluting / Medium
100–150 GSM
1.40 – 1.70
Duplex / Triplex Board
200–400 GSM
1.30 – 1.60
White Top Liner
130–200 GSM
1.10 – 1.25
Newsprint
40–60 GSM
1.50 – 1.80
Coated / Art Paper
80–300 GSM
0.85 – 1.10
❓ Frequently Asked Questions
What is Bulk Factor in paper?
Bulk factor (cc/g) is the reciprocal of paper density — it tells how many cubic centimetres of volume one gram of paper occupies. Higher bulk means bulkier/softer paper. Bulk Factor = 1 ÷ Density (g/cm³).
Why do results say "Approximate"?
Calculation assumes uniform winding tension and constant paper thickness. In practice, winding tension variation and splice points cause minor deviations. Actual weight may vary ±2–5% from calculated values.
What is standard core ID for paper reels?
Most common core inside diameter is 76 mm (3 inches). Some mills use 150 mm (6-inch) cores for very large reels. Core wall thickness typically ranges from 8 mm to 15 mm depending on reel weight.
How to convert Reel Length from metres to feet?
Multiply metres by 3.281 to get feet. Example: 2500 m × 3.281 = 8,202 feet. For yards, multiply metres by 1.094.
Stretch Film Production & Weight Calculators | PropacTools
๐ญ PropacTools — Industrial Calculators
Stretch Film Production & Weight Calculators
Complete professional toolkit for stretch film manufacturers, converters, and packaging engineers — calculate roll weight, yardage, GSM, and more with precision.
Calculate the gross and net weight of a stretch film roll
๐ What is Roll Weight?
Roll weight refers to the total weight of a finished stretch film roll including the plastic core. In stretch film production, knowing the precise roll weight is critical for inventory management, transportation cost calculation, and customer billing. Net weight is the weight of film only (without core).
Formula:
Core OD (mm) = Core ID + (2 × Wall Thickness)
Volume (cm³) = (ฯ ÷ 4) × [(OD/10)² − (CoreOD/10)²] × (Width/10)
Film Wt (kg) = Volume × Density ÷ 1000
Gross Wt (kg) = Film Wt + Core Wt
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Film Length (m) = (ฯ ÷ 4) × (OD² − CoreOD²) ÷ Micron × 1000 [all in mm, ยตm]
Enter Roll OD, Core ID + Wall Thickness (OD auto-filled), Film Width, Micron (thickness in ยตm), and Density. Calculator gives both Roll Weight (from geometry+density) and Film Length in meters (from geometry+micron). Core weight field is optional — use Core Weight Calculator below.
⚖️
Roll Weight Calculator
in mm (full roll OD)
in mm — 3-inch=76mm, 2-inch=52mm
in mm → Core OD = ID + 2×Wall
mm — read only
in mm
in ยตm — e.g. 17, 20, 23 micron
g/cm³ (LLDPE default: 0.920)
in kg — use Core Weight Calculator below
๐ Results
Film Type
Density (g/cm³)
Standard Width
Typical Thickness
LLDPE Stretch Film
0.918 – 0.922
500mm / 450mm
17–23 microns
HDPE Stretch Film
0.940 – 0.960
500mm
10–15 microns
PP Stretch Film
0.900 – 0.910
500mm
20–25 microns
Pre-Stretch Film
0.918 – 0.922
500mm
8–12 microns
๐
2. Film Length / Yardage Calculator
Calculate total meters of film on a roll
๐ Why Calculate Film Length?
Film length (also called yardage) determines how many wraps a roll can provide on a pallet. It is specified in customer orders, and directly affects the price per meter. The length is calculated from the roll geometry and film thickness.
Core OD (mm) = Core ID + (2 × Wall Thickness)
Thickness (mm) = Micron ÷ 1000
Length (mm) = (ฯ ÷ 4) × (Roll OD² − Core OD²) ÷ Thickness_mm
Length (m) = Length (mm) ÷ 1000
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Width cancels out — Length depends only on Roll OD, Core OD, and Micron.
Enter Micron directly (e.g. 20). Core OD is auto-calculated from Core ID + Wall Thickness. No manual OD needed.
๐
Film Length Calculator
in mm (full roll OD)
in mm — 3-inch=76mm, 2-inch=52mm
in mm
OD = ID + (2 × Wall) — read only
in ยตm — e.g. 17, 20, 23 micron
๐ Results
๐ฌ
3. GSM & Thickness Calculator
Convert between GSM, thickness (micron), and density
๐ Understanding GSM and Micron
GSM (Grams per Square Meter) is the weight per unit area of film. Micron (ยตm) is the thickness unit (1 micron = 0.001 mm = 0.000001 m). Both are interchangeable using density:
GSM = Thickness (micron) × Density (g/cm³)
Thickness (micron) = GSM ÷ Density (g/cm³)
Example: 20 micron LLDPE = 20 × 0.920 = 18.4 GSM
๐ฌ
GSM / Thickness Converter
Enter micron or GSM value
g/cm³
๐ Results
๐งป
4. Cardboard Core Weight Calculator
Estimate the weight of paper/cardboard cores
๐ Core Weight Importance
The cardboard core (tube) adds to gross roll weight. Knowing core weight allows accurate net film weight calculation, which affects pricing and specification compliance. Standard stretch film cores are 3-inch (76mm OD), 2-inch (52mm OD). Cardboard density ≈ 1.0–1.2 g/cm³.
Enter ID (Inner Diameter) and Wall Thickness. OD auto-fills. Paper/cardboard core density ≈ 0.65–0.80 g/cm³ (default 0.73) — NOT 1.10 which is solid material density.
๐งป
Core Weight Calculator
in mm — 3-inch=76mm, 2-inch=52mm
in mm
OD = ID + (2 × Wall) — read only
in mm — same as film width
g/cm³ — paper core: 0.65–0.80 (default 0.73)
๐ Results
๐ญ
5. Production Output Calculator
Calculate daily/shift kg output from extruder line speed
๐ Line Speed to Output Conversion
In stretch film extrusion, the line speed (meters per minute or m/min) combined with film dimensions determines how many kilograms of film are produced per hour or per shift. This helps plan production schedules and raw material consumption.
Output (kg/hr) = Line Speed (m/min) × 60 × Width (m) × Thickness (m) × Density (g/cm³) × 1000
๐ญ
Production Output Calculator
meters per minute (m/min)
in mm
in microns (ยตm)
g/cm³
hours per shift
machine utilization %
๐ Results
๐ฐ
6. Material Cost Calculator
Calculate cost per kg and per roll of stretch film
๐ Cost Estimation
Material cost calculation helps manufacturers set selling prices, analyze margins, and plan procurement. It accounts for resin cost, conversion cost, and target roll weight to arrive at a per-roll cost.
Cost per Roll = Roll Net Weight (kg) × (Resin Cost + Conversion Cost) per kg
๐ฐ
Material Cost Calculator
kg (film only, no core)
per kg (USD/INR/any currency)
per kg (energy + labor + overhead)
per piece
desired profit margin
optional (e.g. ₹, $, €)
๐ Results
๐ช
7. Stretch Ratio & Elongation Calculator
Calculate stretch ratio, pre-stretch %, and effective gauge
๐ Stretch Ratio & Pre-Stretch
Stretch film is stretched during application (hand wrap or machine wrap). The stretch ratio determines how much the film elongates. Pre-stretch (on machine wraps) can extend film up to 250–300% of its original length, reducing material cost per pallet.
Stretch % = [(Stretched Length − Original Length) / Original Length] × 100
Effective Thickness (ยตm) = Original Thickness ÷ (1 + Stretch% / 100)
Effective GSM = Original GSM ÷ (1 + Stretch% / 100)
๐ช
Stretch Ratio Calculator
in microns (ยตm)
in meters
in meters
g/m² (optional)
๐ Results
๐งช
8. Resin Quantity & Raw Material Calculator
Calculate resin needed for a production run
๐ Resin Planning
Before a production run, manufacturers need to know exactly how much resin (LLDPE, HDPE, metallocene, etc.) is required. This calculator accounts for scrap/waste percentage and gives total resin purchase quantity for the run.
Net Resin (kg) = No. of Rolls × Net Roll Weight (kg)
Gross Resin (kg) = Net Resin ÷ (1 − Waste% / 100)
Calculate output metres, number of rolls, raw material cost & profit — from a single kraft paper input roll.
What is Honeycomb Paper (Cushioning Wrap)?
Honeycomb paper — also called paper bubble wrap or honeycomb cushioning wrap — is an eco-friendly alternative to plastic bubble wrap. It is made from a single sheet of kraft paper that is die-cut with staggered slits and then expanded to form a hexagonal honeycomb pattern. The expanded roll provides excellent cushioning, void-fill, and surface protection.
Unlike multi-layer corrugated board, honeycomb cushioning wrap is a single-layer product. The magic is entirely in the cut-and-expand process — no lamination, no glue, no heat required.
๐ฆ Material
Kraft paper — 40 to 80 GSM. Lighter GSM = more metres per kg. Heavier GSM = stronger cushioning.
The core formula is simple — but many manufacturers get it wrong due to unit mismatch:
Flat Paper Length (m) = Roll Weight (g) ÷ [ GSM × Width (m) ] Expanded Length (m) = Flat Paper Length × Expansion Ratio Usable Length (m) = Expanded Length × (1 − Wastage % / 100) Output Rolls = floor ( Usable Length ÷ Output Roll Length ) Roll Weight (kg) = Usable Paper Weight ÷ Number of Rolls
Important: Expansion only increases length — not weight. 1 metre of flat paper becomes 1.8 metres of honeycomb, but the paper weight stays exactly the same. Roll weight = usable kg ÷ number of rolls.
Worked Example
Input Parameter
Value
Result
Roll weight
50 kg = 50,000 g
—
GSM × Width
60 × 0.3 m = 18
—
Flat paper length
50,000 ÷ 18
2,778 metres
After expansion (1.8×)
2,778 × 1.8
5,000 metres
Usable (8% wastage)
5,000 × 0.92
4,600 metres
Output rolls (50 m each)
4,600 ÷ 50
92 rolls
Roll weight
46 kg ÷ 92 rolls
0.5 kg per roll
Expansion Ratio — What Does It Mean?
The expansion ratio tells you how many times the final expanded roll is longer than the original flat paper. A ratio of 1.8× means 1 metre of flat kraft paper becomes 1.8 metres of honeycomb wrap after expansion.
Ratio
Cell Size
Best For
1.5×
Tight / small
Heavy items, strong wrapping needed
1.8×
Standard
General e-commerce packaging (most common)
2.2×
Wide
Light fragile items, jewellery, glassware
2.5×
Maximum
Very light goods, maximum yield per kg
Choosing the Right GSM for Kraft Paper
GSM (Grams per Square Metre) is the key variable that controls both the strength of your product and the number of metres you get per kilogram of input paper.
GSM
Metres per kg (300mm wide)
Recommended Use
40 GSM
83.3 m/kg
Lightweight items only
50 GSM
66.7 m/kg
Light e-commerce
60 GSM
55.6 m/kg
Standard — most popular
80 GSM
41.7 m/kg
Heavy goods, fragile items
100 GSM
33.3 m/kg
Export, premium cushioning
120 GSM
27.8 m/kg
Heavy industrial packaging, auto parts
140 GSM
23.8 m/kg
Maximum strength — heavy machinery, export heavy goods
Who Uses This Calculator?
๐ญ Manufacturers Plan raw material purchase per production shift
๐ E-commerce Sellers Calculate how many rolls needed per 1,000 orders
๐ฆ Distributors Price per roll vs raw material cost analysis
๐งพ Purchase Managers Verify supplier quotes against actual output
▶ How many metres of honeycomb wrap comes from 1 kg of kraft paper (60 GSM, 300mm wide)?
Using the formula: 1000g ÷ (60 GSM × 0.3m) = 55.6 metres of flat paper. After 1.8× expansion, you get approximately 100 metres of honeycomb wrap per kg — before wastage deduction.
▶ What is a typical machine wastage percentage?
Semi-automatic machines: 8–12%. Fully automatic machines: 4–7%. Manual operations: 10–15%. Use 8% as a safe default for planning purposes.
▶ Is honeycomb wrap the same as corrugated board?
No. Corrugated board is multi-layer (liner + fluted medium + liner) made with starch adhesive. Honeycomb cushioning wrap is a single layer of kraft paper, die-cut and mechanically expanded. No glue or lamination involved.
▶ What is a standard output roll length for honeycomb wrap?
Common output lengths are 25m, 50m, and 100m depending on target market. E-commerce sellers prefer 50m rolls. Bulk industrial buyers prefer 100m. Retail/gifting formats are 25m or smaller.
▶ Does expansion increase the weight of the roll?
No. Expansion only increases length — not weight. 1 metre of flat paper becomes 1.8 metres of honeycomb, but the paper mass stays the same. Roll weight = usable kg ÷ number of rolls.
