Plastic Film Thickness and Weight Calculator
Accurately calculate roll weight, yield, and dimensions for industrial films.
LDPE (Low Density Polyethylene)
HDPE (High Density Polyethylene)
LLDPE (Linear Low Density PE)
PP (Polypropylene)
PET (Polyester)
PVC (Rigid)
PVC (Flexible)
Nylon (PA)
Custom Density
Select the polymer type to auto-fill density.
Specific gravity of the material.
Please enter a valid positive density.
Microns (µm)
Mils (0.001″)
Millimeters (mm)
Gauge
Please enter a valid thickness.
Millimeters (mm)
Centimeters (cm)
Meters (m)
Inches (in)
Please enter a valid width.
Meters (m)
Feet (ft)
Yards (yd)
Please enter a valid length.
Total Net Weight
46.00 kg
(Excluding core weight)
Weight per Roll:
46.00 kg
Total Weight (lbs):
101.41 lbs
Yield (Area per kg):
21.74 m²/kg
Total Area:
500.00 m²
Specification Summary
| Parameter | Value |
|---|
Weight Sensitivity Analysis (Thickness Variation)
Shows how total weight changes if thickness varies by ±20%.
What is a Plastic Film Thickness and Weight Calculator?
A plastic film thickness and weight calculator is an essential engineering tool used by packaging professionals, manufacturers, and procurement specialists to determine the theoretical mass of plastic films based on their physical dimensions and density. Whether you are working with LDPE, HDPE, PET, or PVC, understanding the exact weight of a roll is critical for logistics planning, cost estimation, and quality control.
Unlike generic volume calculators, this tool is specifically calibrated for the flexible packaging industry. It accounts for the specific gravity (density) of different polymers and handles the complex unit conversions often found in the industry, such as converting between microns, mils, and gauge for thickness, or meters and feet for length.
Common misconceptions include assuming all plastics have the same weight per meter. In reality, a roll of PET film will be significantly heavier than a roll of PP film of the exact same dimensions due to density differences (1.38 g/cm³ vs 0.90 g/cm³).
Plastic Film Weight Formula and Mathematical Explanation
The core physics behind the plastic film thickness and weight calculator relies on the relationship between volume and density. To find the weight, we first calculate the volume of the material and then multiply it by the polymer's density.
Weight (kg) = Length (m) × Width (m) × Thickness (mm) × Density (g/cm³)
However, because industry units vary wildly (microns for thickness, meters for length, millimeters for width), the formula requires strict unit normalization. Here is the step-by-step derivation used in this tool:
- Normalize Dimensions: Convert Length ($L$) to meters, Width ($W$) to meters, and Thickness ($T$) to millimeters.
- Calculate Volume: $Volume = L \times W \times (T / 1000)$. This gives volume in cubic meters ($m^3$).
- Apply Density: Since density ($\rho$) is usually given in $g/cm^3$, we convert it to $kg/m^3$ by multiplying by 1000.
- Final Calculation: $Mass = Volume (m^3) \times Density (kg/m^3)$.
Variable Reference Table
| Variable | Meaning | Common Unit | Typical Range |
|---|---|---|---|
| L | Length of the film roll | Meters (m), Feet (ft) | 500m – 10,000m |
| W | Width of the web | mm, inches | 100mm – 2000mm |
| T | Thickness (Gauge) | Micron (µm), Mil | 10µm – 250µm |
| $\rho$ (Rho) | Density (Specific Gravity) | g/cm³ | 0.90 – 1.40 |
Practical Examples (Real-World Use Cases)
Example 1: Standard Pallet Wrap (LLDPE)
A warehouse manager needs to know the weight of a standard hand stretch wrap roll to estimate shipping costs.
- Material: LLDPE (Density: 0.92 g/cm³)
- Width: 500 mm
- Length: 400 meters
- Thickness: 20 microns
Calculation:
Volume = 400m × 0.5m × 0.00002m = 0.004 m³
Weight = 0.004 m³ × 920 kg/m³ = 3.68 kg per roll.
Example 2: Heavy Duty Construction Film (LDPE)
A construction firm is ordering vapor barriers and needs to check if the delivered weight matches the specifications.
- Material: LDPE (Density: 0.92 g/cm³)
- Width: 20 feet (approx 6.096m)
- Length: 100 feet (approx 30.48m)
- Thickness: 6 mil (approx 152.4 microns)
Result: Using the calculator, this configuration yields a weight of approximately 26.05 kg (57.4 lbs).
How to Use This Plastic Film Thickness and Weight Calculator
- Select Material: Choose your polymer from the dropdown (e.g., LDPE, PET). The density field will auto-populate. If you have a custom blend, select "Custom" and enter the specific gravity from your technical data sheet (TDS).
- Enter Dimensions: Input the thickness, width, and length. Be careful to select the correct units (e.g., if your spec sheet says "50 gauge", select "Gauge" in the unit dropdown).
- Set Quantity: If you are calculating for a full pallet or order, increase the number of rolls.
- Analyze Results: The tool immediately displays the Net Weight. Use the "Yield" metric to understand how much area you get per kilogram of resin.
- Check Sensitivity: Look at the chart to see how slight variations in thickness (gauge bands) might affect the total weight of your order.
Key Factors That Affect Plastic Film Results
When using a plastic film thickness and weight calculator, consider these financial and physical factors that influence the final numbers:
- Density Variations: Even within "LDPE", density can range from 0.915 to 0.930 depending on the resin grade. A 0.01 difference in density changes the weight by roughly 1%.
- Additives and Masterbatches: Films are rarely pure resin. Adding UV stabilizers, slip agents, or heavy color masterbatches (like Titanium Dioxide for white film) increases the density, making the roll heavier than the theoretical calculation.
- Gauge Variation (Thickness Profile): Extrusion is not perfect. A film sold as "50 micron" might average 52 microns across the web, resulting in "giveaway" weight that costs the manufacturer money.
- Core Weight: This calculator provides Net Weight (film only). For shipping weight (Gross Weight), you must add the weight of the cardboard or PVC core, which can range from 0.5kg to over 5kg depending on wall thickness.
- Scrap and Trim: If you are calculating resin requirements for production, remember to add a percentage for edge trim and startup waste (typically 3-10%).
- Cost Implications: Plastic is sold by weight (kg/lb) but used by area (packaging coverage). A lower density film (like PP vs PET) offers a better "Yield," meaning you get more packaging wrappers per kilogram of material purchased.
Frequently Asked Questions (FAQ)
What is the difference between Micron, Mil, and Gauge?
These are all units of thickness. 1 Mil = 0.001 inches = 25.4 Microns. Gauge is typically Mil × 100 (e.g., 100 Gauge = 1 Mil). This calculator handles all conversions automatically.
Does this calculator include the weight of the core?
No, this tool calculates the Net Weight of the plastic film only. You must weigh your core separately and add it to get the Gross Weight.
Why is my actual roll heavier than the calculated weight?
This is usually due to "average thickness" being higher than the target specification, or the presence of heavy additives like anti-block or white pigment which increases density.
How do I calculate Yield?
Yield is the area of film per unit of weight. The formula is: $Yield (m^2/kg) = 1000 / (Thickness(\mu m) \times Density)$. A higher yield means more film area for the same cost.
What is the density of standard clear plastic?
For standard clear bags (LDPE), use 0.92 g/cm³. For crinkly clear bags (PP), use 0.90 g/cm³. For clear water bottles or rigid sheets (PET), use 1.38 g/cm³.
Can I use this for rigid sheets?
Yes, as long as the material is uniform. The math for a thin film and a thick rigid sheet is identical; just ensure your thickness input is correct.
How accurate is this calculator?
It is mathematically precise based on the inputs provided. However, real-world manufacturing tolerances usually result in a variance of ±3% to ±5%.
Why is Yield important for purchasing?
If you buy film by the kg but sell your product by the unit, a film with better yield (lower density or thinner gauge) reduces your per-unit packaging cost directly.
Related Tools and Resources
- GSM to Thickness Calculator – Convert Grams per Square Meter to microns.
- Roll Diameter Calculator – Estimate the outer diameter of a roll based on length and thickness.
- Resin Cost Estimator – Calculate the raw material cost for extrusion runs.
- Cubic Meter (CBM) Calculator – Calculate shipping volume for pallets.
- Shrink Wrap Yield Calculator – Specific tool for heat shrink packaging analysis.
- Paper Weight Conversion Tool – Compare plastic film weights to paper basis weights.