Poly Roll Weight Calculator
Instantly calculate the weight, diameter, and shipping metrics for polyethylene film rolls.
Assumes LDPE Density ≈ 0.92 g/cm³ (0.0332 lbs/in³).
Weight vs. Length Projection
Roll Specification Breakdown
| Length (ft) | Weight (lbs) | Diameter (in) |
|---|
*Diameter estimates assume tight winding and standard 3″ core.
What is a Poly Roll Weight Calculator?
A poly roll weight calculator is an essential tool for packaging engineers, logistics managers, and procurement specialists in the plastics industry. It determines the theoretical weight of a roll of polyethylene (poly) film based on its physical dimensions—width, length, and thickness (gauge)—and the specific density of the material.
Whether you are dealing with Layflat Tubing, Centerfold Sheeting, or Single Wound Sheeting, knowing the exact weight of a roll is critical for calculating shipping costs, managing inventory, and ensuring machinery compatibility. This calculator uses the standard density of Low-Density Polyethylene (LDPE), the most common material used in industrial poly bags and films.
Poly Roll Weight Formula and Mathematical Explanation
The calculation of poly roll weight is based on the volume of the plastic material multiplied by its density. While there are simplified "industry factors" often used for quick estimates, the most accurate method involves calculating the cubic volume of the plastic.
The Core Formula
The fundamental physics formula used is:
Weight (lbs) = Volume (in³) × Density (lbs/in³)
Where:
- Volume = Width (in) × Length (in) × Thickness (in) × Layers
- Density = ~0.0332 lbs/in³ (Derived from 0.92 g/cm³ for LDPE)
Variables Table
| Variable | Meaning | Unit | Typical Range |
|---|---|---|---|
| Width | Face width of the roll | Inches | 2″ – 120″ |
| Length | Total linear footage | Feet | 500′ – 5000′ |
| Gauge | Thickness of the film wall | Mil (0.001″) | 0.5 – 10 Mil |
| Layers | Material plies (Tubing = 2) | Count | 1 or 2 |
Practical Examples (Real-World Use Cases)
Example 1: Standard Poly Tubing
A warehouse manager needs to ship a pallet of 6 Mil poly tubing. The roll is 12 inches wide and has 1,000 feet of material.
- Input: 12″ Width, 1000′ Length, 6 Mil, Tubing (2 layers).
- Calculation:
Volume = 12 × (1000 × 12) × (0.006) × 2 = 1,728 in³
Weight = 1,728 in³ × 0.0332 lbs/in³ - Result: ~57.4 lbs per roll.
Example 2: Thin Construction Sheeting
A construction supplier is verifying the weight of a large roll of Single Wound Sheeting (SWS) used for vapor barriers.
- Input: 96″ Width, 100′ Length, 4 Mil, Single Layer.
- Calculation:
Volume = 96 × (100 × 12) × (0.004) × 1 = 460.8 in³
Weight = 460.8 in³ × 0.0332 lbs/in³ - Result: ~15.3 lbs per roll.
How to Use This Poly Roll Weight Calculator
- Enter Roll Width: Input the width of the roll face in inches. If it is gusseted tubing, use the flat width.
- Enter Length: Input the total length of the film in feet.
- Select Thickness: Enter the gauge in Mils. (e.g., for 2 mil, enter 2).
- Select Film Type: Choose "Tubing" or "Centerfold" if the film is double-layered on the roll. Choose "Single Wound" for a single sheet.
- Review Results: The calculator instantly updates the total weight and estimates the outer diameter of the roll based on a standard 3-inch core.
Key Factors That Affect Poly Roll Weight Results
Understanding the variables that influence the final weight is crucial for accurate logistics planning.
1. Material Density (Resin Type)
This calculator assumes Low-Density Polyethylene (LDPE), which has a density of roughly 0.92 g/cm³. High-Density Polyethylene (HDPE) is denser (approx. 0.95 g/cm³), which would result in a slightly heavier roll for the same dimensions.
2. Gauge Consistency
Manufacturing tolerances mean that a "4 Mil" film might actually average 3.8 or 4.2 Mils. A 10% variation in thickness results in a 10% variation in total weight.
3. Film Type (Layers)
The most common error in using a poly roll weight calculator is ignoring the layers. Tubing and Centerfold sheeting effectively have two layers of plastic for every inch of width. Failing to account for this will result in calculating only half the actual weight.
4. Core Weight
The cardboard core adds static weight. While a standard 3-inch core is light, heavy-duty cores for large industrial rolls can add 2-5 lbs to the gross weight.
5. Additives
Films with additives like UV inhibitors, anti-static agents, or color concentrates (masterbatch) may have slightly different densities than virgin clear LDPE.
6. Winding Tension
While tension doesn't change the weight, it drastically affects the roll diameter. Tightly wound rolls are smaller; loose rolls are larger. Our diameter calculation assumes a solid, void-free wind.
Frequently Asked Questions (FAQ)
This tool is optimized for LDPE/LLDPE. For HDPE, add approximately 3-4% to the final weight. For Polypropylene (PP), subtract about 2% as it is slightly less dense.
In the plastics industry, "Mil" refers to one-thousandth of an inch (0.001″). Sometimes "Gauge" is used where 100 Gauge = 1 Mil. This calculator uses Mil.
For gusseted bags or tubing, use the total flat width (Face Width + Depth of Gusset) as the "Roll Width" input to get the accurate material weight.
Variations usually stem from gauge inconsistency (average thickness variation) or the weight of the cardboard core and packaging, which are not included in the net plastic weight.
Yes, you can reverse the math. If you know the weight, divide it by the weight-per-foot (derived from width and thickness) to find the total length.
The industry standard for most hand and machine rolls is a 3-inch inner diameter (ID) cardboard core.
Generally, no. The pigment constitutes a very small percentage of the total volume, so the density change is negligible for standard shipping calculations.
Stretch wrap is often LLDPE but is stretched during application. For the roll weight itself (unstretched), this calculator is accurate if you know the gauge and length.
Related Tools and Internal Resources
Explore more tools to assist with your packaging and logistics planning:
- Poly Bag Gauge Calculator – Determine the right thickness for your application.
- Pallet Configuration Tool – Optimize your pallet stacking for shipping.
- Freight Class Calculator – Estimate shipping classes based on density.
- Stretch Wrap Usage Calculator – Calculate film needed per pallet.
- Box Volume Calculator – Calculate cubic footage for packaging.
- Dimensional Weight Calculator – Compare actual weight vs. DIM weight.