Advice & investment
How to calculate stretch film roll length and weight
Written by Öncümak Engineering Team2 min read
In short
The net film weight of a roll is length × width × thickness × density. With LLDPE's density of about 0.92 g/cm³, a 50 cm wide, 20 µm film weighs about 9.2 g per metre, so a 300 m hand roll holds about 2.8 kg of film. The formula lets you compare offers and check what you are actually buying.
All topics
Stretch film basics
- What is stretch film?
- Hand vs machine stretch film: what's the difference?
- What is pre-stretched film?
- What is coreless stretch film?
- PE stretch film vs PVC cling film: what's the difference?
- Is stretch film recyclable?
- Where is slit stretch film used?
- Black and coloured stretch film: what is the colour for?
- Why stretch film tears, breaks or does not cling, and how to fix it
- How to wrap a pallet with stretch film
- How many pallets does a roll of stretch film wrap? Film use and cost per pallet
- Stretch film vs shrink film: what is the difference?
- How to use coreless stretch film: handles, dispensers and wrapping machines
- When is pre-stretched film not the right choice?
- How to measure the pre-stretch on a pallet wrapper
- Stretch hood vs stretch wrap: which one fits your pallets?
- How wrapped pallets are tested: load stability and EUMOS 40509
- Recycled content (PCR) stretch film and plastic packaging taxes
- How to store stretch film: temperature, humidity and shelf life
- One-sided vs two-sided cling stretch film
- UV-resistant stretch film for outdoor storage
- Stretch film for moving house: how to wrap furniture and boxes
- Slit stretch film, strapping or tape: which one for bundling?
- Which width for which product? Slit stretch film rolls and dispensers
Advice & investment
- How to choose a stretch film rewinding machine
- How to calculate stretch film roll length and weight
- Stretch film thickness: what do the microns change?
- How much does a stretch film rewinding machine produce?
- How to start a stretch film rewinding business
- How to choose jumbo rolls for stretch film rewinding
- What determines the price of stretch film?
The formula
Net film weight (kg) = length (m) × width (m) × thickness (µm) × density (g/cm³) ÷ 1000
And the other way round:
Length (m) = net film weight (kg) × 1000 ÷ (width (m) × thickness (µm) × density (g/cm³))
For polyethylene stretch film a density of 0.92 g/cm³ is a good working value.
Worked examples
| Width | Thickness | Length | Net film weight |
|---|---|---|---|
| 50 cm | 20 µm | 300 m | ≈ 2.76 kg |
| 50 cm | 17 µm | 300 m | ≈ 2.35 kg |
| 50 cm | 8 µm | 300 m | ≈ 1.10 kg |
| 50 cm | 23 µm | 1500 m | ≈ 15.9 kg |
For example, 0.5 m × 20 µm × 0.92 ÷ 1000 = 0.0092 kg, or about 9.2 g per metre, so 300 m weigh about 2.76 kg. In reverse, 2.5 kg of 50 cm, 20 µm film is about 2.5 × 1000 ÷ (0.5 × 20 × 0.92) ≈ 272 m.
Density
LLDPE is the main raw material of stretch film. ASTM D4635, the US standard specification for LDPE and LLDPE packaging films, covers films with densities of 0.910–0.925 g/cm³. Within that range, using 0.92 changes the result by about one percent at most, far less than the effect of thickness.
Don't forget the core
A roll's gross weight includes its paper core. To find the net film weight, weigh an empty core of the same type and subtract it. Coreless rolls have no core, so their gross weight is their net film weight, which is why price comparisons should be made per kilogram of net film. See coreless stretch film.
Microns and gauge
Thickness is given in microns (µm) in most of the world. In North America it is often given in gauge: 100 gauge = 1 mil = 25.4 µm, so 80 gauge ≈ 20 µm and 60 gauge ≈ 15 µm.
Why real rolls differ slightly
Film thickness has a production tolerance, density varies with the grade, and cores differ in weight. Expect small differences between the calculation and the scale; large ones mean the roll is shorter or thinner than stated.
Sources(3)
- ASTM D4635-25, Standard Specification for Plastic Films Made from Low-Density Polyethylene and Linear Low-Density Polyethylene for General Use and Packaging Applications. ASTM
- AAA Polymer. Stretch film micron vs gauge
- Carepac. Gauge to mil to micron conversion
Related machines
- How to choose a stretch film rewinding machineStart from the rolls you want to sell, not from the machine: the roll type, the widths, your volumes and the jumbo rolls you can buy decide which rewinder fits. Then compare speed, tension control, core sizes and after-sales support, and look at the total cost, not only the price.
- Stretch film thickness: what do the microns change?Thickness decides how many metres of film you get per kilo, how well the film resists punctures and what it costs per pallet, but it does not decide on its own how well a load is held. Film quality and how far the film is stretched matter just as much.
- How much does a stretch film rewinding machine produce?Theoretical hourly and monthly output of Öncümak's rewinding machines, with every assumption behind the figures, and the factors that make real production higher or lower.
- How to start a stretch film rewinding businessA rewinding business buys jumbo rolls from film producers, rewinds them into the rolls its market buys and sells them under its own name. To start, you need customers who buy a clear set of roll types, a steady supply of jumbo rolls and cores, a rewinding machine that matches those rolls, a 400 V three-phase supply, storage space, trained operators and simple quality checks.
- How to choose jumbo rolls for stretch film rewindingThe jumbo roll decides what your finished rolls can be. First check that its width, weight and thickness fit your machine; then look at cast or blown film, cling, stretch performance and roll quality. Buy to a written specification, inspect every delivery and run a trial before you order in volume.
- What determines the price of stretch film?Stretch film is sold by weight, so the price of a roll comes down to how many kilograms of film it holds and what each kilogram costs. The cost per kilogram depends on the raw material, the film grade and any extras such as colour, UV protection or recycled content; the roll format and the order size add to it. Compare offers by the price per kilogram of net film and by the cost per pallet, not by the price per roll.