Calculate stretch film weight, roll length, film width, or thickness from any three values, with gauge, mil, micron, metric, imperial, density, and core-weight options.

Uniform, as-supplied film. Default density: 0.920 g/cm³ for representative LLDPE; supplier data prevails.

Material density

0.920 is representative LLDPE. Blank uses 0.920; supplier density prevails.

Stretch Film Weight Guide

The stretch film weight calculator estimates net film mass from length, width, thickness and density, or solves for one missing dimension. Gross roll weight adds the entered core mass; reverse gross-weight calculations subtract it first. Use uniform film dimensions in the same as-supplied state, not stretched length with original thickness. The default density, 0.920 g/cm³, is a typical value for a Dow LLDPE stretch-film grade, not a universal film property; supplier density prevails.

Stretch Film Weight Formula

m = ρ × L × W × t
Variable Description SI Unit
m Net film mass kg
L Roll length m
W Roll width m
t Film thickness m
ρ Film density kg/m³

At unchanged density, net film mass changes directly with each dimension. If length, width, or gauge increases, net film mass increases in the same proportion. The calculator converts the selected units to the SI units above before solving.

Rearranged Forms

If one value is unknown, the same formula can be rearranged to solve for it:

L = (m) / (ρ × W × t)
W = (m) / (ρ × L × t)
t = (m) / (ρ × L × W)

What Each Input Means

  • Roll Length: the total length of film on the roll.
  • Roll Width: the width of the film web, measured across the roll.
  • Film Gauge: the thickness specification of the film.
  • Stretch Film Weight: net excludes the core; gross adds the entered core mass automatically. Gross mode requires a core value, including an explicit 0 when no core is included. In a reverse gross-weight solve, known total weight must exceed core weight.

How the Inputs Affect the Result

  • If the roll length doubles, the film weight doubles.
  • If the roll width doubles, the film weight doubles.
  • If the gauge doubles, the film weight doubles.
  • A 10% increase in any one input causes a 10% increase in weight.
  • If two inputs both increase, their effects multiply together.
SFW₂ = SFW₁ × (L₂) / (L₁) × (W₂) / (W₁) × (G₂) / (G₁)

This makes the formula especially helpful when comparing alternate film specifications. For example, reducing gauge lowers weight directly, while increasing width or length raises material usage at the same rate.

Unit Notes

Use the calculator’s input and result unit selectors so each quantity is converted correctly. Film gauge follows the common packaging convention documented in the IPG stretch-film data sheet: 100 gauge = 1 mil = 25.4 µm. A common source of error is mixing gauge and mil values.

1 mil = 100 gauge
1 mil = 0.0254 mm

That means a film listed as 1.5 mil is the same as 150 gauge. If the wrong thickness unit is entered, the calculated weight can be off by a large amount.

Examples

Example 1: Find the film weight

Suppose net film has a length of 120 ft, a width of 30 in, and a gauge of 150, at the default density of 0.920 g/cm³. In SI, these are 36.576 m, 0.762 m, 0.0000381 m and 920 kg/m³.

m = ρ L W t ≈ 0.976931 kg ≈ 2.153765 lb

Example 2: Find the required gauge

If net film must weigh 3 lb, and its length is 200 ft with a width of 20 in, use the same 0.920 g/cm³ density. The reverse thickness equation gives about 47.762879 µm; convert that thickness to gauge:

G = (t (µm)) / (0.254) ≈ 188.042831

So the required film thickness is about 188 gauge.

Common Input Mistakes

  • Entering roll diameter instead of total roll length.
  • Using centimeters while inches is selected, or meters while feet is selected.
  • Entering mil as if it were gauge.
  • Confusing net film mass with gross roll mass, or omitting the required core value in gross mode.
  • Rounding the gauge too early before finishing the calculation.

When This Calculator Is Most Useful

  • Comparing two film options before ordering.
  • Estimating inbound or outbound shipment weights.
  • Checking whether a supplier’s roll specification is reasonable.
  • Planning storage loads and inventory counts.
  • Estimating material use for packaging operations.

Quick Process

  1. Choose the quantity to solve for, then enter the other three values.
  2. Confirm that the selected units match the numbers being entered.
  3. Calculate the missing value.
  4. Review whether the result represents film-only weight or total roll weight with core.

At fixed density, net film mass changes proportionally with each dimension, so this calculator supports fast what-if comparisons of material mass and shipping needs. Actual roll mass can vary, and mass alone does not establish film strength or wrapping performance.