Tools
Film calculator.
Work out the weight, area and yield of plastic film, how much is on a reel, how big a reel will be, and how many sheets make a kilogram, then convert microns, gauge and mil.
- Polymex® polyester density
- 1.40
- Cores we wind onto
- 76 / 152 mm
Film calculator
Weight, area, reel length and sheets.
Choose what you want to work out, then the film and its thickness. Every answer can be copied, or sent to us with a quote request.
Enter the figures above to see the answer.
How to use it
Four steps to an answer.
- 01
Choose what to work out
Weight and area, reel length (or the diameter for a length), length from a reel's weight, sheets, or a thickness conversion.
- 02
Choose the film
Polyester and polypropylene use the densities PSG publishes for Polymex®; for any other film, enter the density from its data sheet.
- 03
Enter the thickness and sizes
Thickness in microns, gauge, mil, millimetres or inches; widths and sheet sizes in millimetres; lengths in metres. A point or a comma is fine for decimals.
- 04
Copy or send the figures
Copy the results into your own notes, or send them to us with a quote request and we will confirm them for your film.
How it works
The formulas behind the figures.
Film is sold by weight and used by area. Weight per square metre (grammage) is the thickness in microns multiplied by the film's relative density, because one micron of film at a density of 1 weighs one gram per square metre. Everything else follows from that and from the size of the film.
Reel length uses the area of the end of the reel (a ring between the core and the outside diameter) divided by the film thickness. Reel lengths and diameters are approximate: the formula assumes tightly wound film, and winding tension, air between the layers and small changes in thickness all make a difference. Check against the reel label or its weight.
Polyester film thickness guideFormulas
t thickness, D reel outside diameter, d core diameter, L length
| Figure | Formula | Units |
|---|---|---|
| Grammage | t × density | t in µm; g/m² |
| Yield | 1,000 ÷ grammage | m²/kg |
| Weight | area × grammage ÷ 1,000 | kg |
| Reel length | π × (D² − d²) ÷ (4 × t) | D, d and t in mm; ÷ 1,000 for metres |
| Outside diameter | √(d² + 4 × L × t ÷ π) | L, d and t in mm |
| Length from weight | net weight ÷ (width × grammage) | kg, m and g/m²; m |
| Sheets per kilogram | 1,000 ÷ (sheet area × grammage) | sheet area in m² |
| Gauge | µm ÷ 0.254 | 100 gauge = 25.4 µm |
| Mil | µm ÷ 25.4 | 1 mil = 0.001 in |
- Grammage
- t × density
- Units: t in µm; g/m²
- Yield
- 1,000 ÷ grammage
- Units: m²/kg
- Weight
- area × grammage ÷ 1,000
- Units: kg
- Reel length
- π × (D² − d²) ÷ (4 × t)
- Units: D, d and t in mm; ÷ 1,000 for metres
- Outside diameter
- √(d² + 4 × L × t ÷ π)
- Units: L, d and t in mm
- Length from weight
- net weight ÷ (width × grammage)
- Units: kg, m and g/m²; m
- Sheets per kilogram
- 1,000 ÷ (sheet area × grammage)
- Units: sheet area in m²
- Gauge
- µm ÷ 0.254
- Units: 100 gauge = 25.4 µm
- Mil
- µm ÷ 25.4
- Units: 1 mil = 0.001 in
Weights are for the film only, not the core or packaging.
A worked example
A 400 mm reel of 23 micron polyester on a 76 mm core.
The film is 1,000 mm wide. These are the figures the calculator gives.
- 01
Grammage
23 µm × 1.40 = 32.2 g/m², so a kilogram covers 1,000 ÷ 32.2 = about 31.06 m².
- 02
Reel length
π × (400² − 76²) ÷ (4 × 0.023) = about 5,266,000 mm, or about 5,266 m of film on the reel.
- 03
Area and weight
1 m wide × 5,266 m = 5,266 m², and 5,266 × 32.2 ÷ 1,000 = about 169.6 kg of film, before the core.
Related
Polyester film, converted to your format.
- Polyester film
Polyester film
Polyester (PET) film
Grades, formats and supply.
- Slitting and sheeting
Converting
Slitting and sheeting
Reels and sheets cut to your specification.
- Film grades
Grades
Polyester film grades
Finishes, treatments and typical thicknesses.
- Thickness guide
Guide
Film thickness explained
Microns, gauge, mil and yield, with a conversion chart.
- Carton window films
Packaging
Carton window films
Clear films for carton windows and packaging.
Common questions
Film calculations, answered.
Why is the reel length approximate?
The formula takes the area of the end of the reel and divides it by the film thickness, which assumes every layer is wound tightly on the one below. Real reels hold a little air between the layers, are wound at different tensions and vary slightly in thickness, so treat the answer as an estimate and check it against the reel label or its weight.
Which density should I use?
Use the figure on your film's data sheet if you have it, with "Other: enter the density". The calculator uses 1.40 for polyester, the relative density PSG publishes for Polymex® polyester, and 0.91 for polypropylene, from the 0.91 to 0.95 PSG publishes for Polymex® polypropylene. The other films are typical published values, not PSG data.
Which core diameter should I enter?
Cores are named by their inside diameter: PSG winds onto 76 mm (3 inch) and 152 mm (6 inch) cores. The film starts on the outside of the core, so if you know the core's outside diameter, enter that for a closer answer.
What is the difference between microns, gauge and mil?
A micron is a thousandth of a millimetre. 100 gauge is 25.4 microns, so a 23 micron film is usually called 92 gauge. A mil is a thousandth of an inch, also 25.4 microns. Our polyester film thickness guide explains each unit, with a conversion chart.
Does the weight include the core?
No. Weights are for the film only. When you work out length from a reel's weight, enter the core weight too and the calculator takes it off first.
Can PSG slit or sheet film to these figures?
Yes. We slit, rewind and sheet polyester film to your width, length or diameter and core size, from our film or yours. Copy your figures into a quote request and we will confirm them for your film.
Need film slit or sheeted to size?
Send us your figures and your specification, and our team will come back to you with a quotation.
