About this calculator

Estimate original film roll length from measured net material mass, original width, thickness and material density. Subtract the core and other non-film tare before converting mass to solid-film volume.

Inputs

How to use this calculator

Roll scenario

  1. Gross roll weight (lb)Measured roll including core and other non-film tare.
  2. Core and other non-film tare (lb)Must be less than the gross roll weight.
  3. Original film width (in)Unstretched roll width, not width on the wrapped load.
  4. Original film thickness (mil)U.S. thickness uses mil (0.001 in); metric uses micrometers. This is not a generic gauge field.
  5. Film material density (g/cm³)Enter the supplier/measured value. 0.92 is illustrative and not assumed correct for your resin or layers.

Enter the shipment or scenario values, then select Calculate result.

Method

Formula and variables

Net film mass = gross roll mass − non-film tare. Length (m) = net kg ÷ [density (g/cm³) × 1,000 × original width (m) × original thickness (µm) × 10⁻⁶]. 1 mil = 25.4 µm. Scenarios are independent.

Gross roll weight (lb)
Measured roll including core and other non-film tare.
Core and other non-film tare (lb)
Must be less than the gross roll weight.
Original film width (in)
Unstretched roll width, not width on the wrapped load.
Original film thickness (mil)
U.S. thickness uses mil (0.001 in); metric uses micrometers. This is not a generic gauge field.
Film material density (g/cm³)
Enter the supplier/measured value. 0.92 is illustrative and not assumed correct for your resin or layers.

Interpret the result

The length is before stretching. It assumes uniform solid film and known material properties, so variation in caliper or density can change the physical roll length.

Outputs: Net film mass and estimated original roll length

Uniform, solid film of known original width, thickness and density. No stretch multiplier, gauge convention, air gaps, thickness variation, nonuniform layers or effective usability is inferred. Estimated physical length may differ from a labeled or measured roll. No material density is verified for you.

Worked example

Check the arithmetic

This example uses the starting values shown above. The arithmetic below is calculated independently of the interactive result.

Work through the calculation

  1. Net film = (11 − 1) × 0.45359237 = 4.5359237 kg.
  2. Width = 20 × 0.0254 = 0.508 m; thickness = 0.8 × 25.4 = 20.32 µm; density = 0.92 × 1,000 = 920 kg/m³.
  3. Length = 4.5359237 ÷ (920 × 0.508 × 20.32 × 0.000001) = 477.6287905 m = approximately 1,567.023591 ft.

Compare the displayed result

Expected displayed result: 1,567.024 ft

FAQs

Is mil the same as a generic film gauge?

This tool uses mil, meaning 0.001 inch. It does not infer a supplier’s gauge convention. Metric mode uses micrometers, and 1 mil equals 25.4 µm.

Example inputs and options

Starting values are examples unless a field identifies a dated rule. Unit selectors convert only fields marked for conversion. Rates and model options keep the units and basis shown in their labels.

Gross roll weight (lb)
Example: 11
Core and other non-film tare (lb)
Example: 1
Original film width (in)
Example: 20
Original film thickness (mil)
Example: 0.8
Film material density (g/cm³)
Example: 0.92