Remaining Film on Roll Calculator
Estimate remaining film length and area from the current roll diameter. Add GSM to translate that balance into estimated net film weight.
Use a saved product specification (optional)
Enter your values
First time using this calculator?
Replace the example values with figures from your supplier sheet or measurements. Choose the unit beside each value. Results update as you type; fix any highlighted field before using the result.
GSM means grams per square metre. Net weight excludes the core and other packaging. MOQ means the minimum order quantity. An optional field can stay blank unless the result you need depends on it.
Prices keep the selected currency; changing its label does not convert an exchange rate. Save or export the result after checking your inputs.
Measure the outside of the core, not its bore.
Help with film thickness
Use the measured or specified material thickness. One micron (µm) is one thousandth of a millimetre.
Help with web width
Measure the full width of the flat material from edge to edge, rather than the width of one finished pack. Choose the matching unit.
Additional measurements (optional) — some values entered
These are only needed for additional result units or a more detailed estimate. Entered values still affect the result when this section is closed.
Use actual supplier or measured GSM when available.
Help with film gsm
GSM is the weight of one square metre of material, in grams. Find it on the supplier specification; use the complete laminate value for layered film.
Estimated remaining length
Geometric estimate: assumes uniform thickness, a tightly wound roll and no entrained air. Actual running length may differ.
Core OUTER diameter is used; a nominal core bore is not a substitute.
Remaining length = π × (current OD² − core OD²) ÷ (4 × thickness)
π × (350² − 90²) ÷ (4 × 80) = 1,123.119374 m; × 0.8 = 898.4954989 m²Saved calculations stay in this browser. No account or cloud backup is created.
Save to a product project (optional)
Choose or create a saved product project ↗This is an illustrative example. Saved or transferred values must be checked against your job.
Calculated from your inputs. Confirm specifications with your supplier.
How sensitive is this result to your assumptions?
Vary one input and inspect estimated remaining length
All other entered inputs stay fixed. Ranges are your scenarios, not statistical confidence or supplier performance predictions. This uses the same validated calculator engine.
The formula, made clear.
The remaining film occupies the annulus between the current roll surface and the core outside surface. Because cross-sectional area depends on diameter squared, a roll that looks half its original diameter does not necessarily contain half its original length. This is a useful stock or run-planning estimate when no reliable length counter is available. The winding estimate requires current roll OD above core OD; an empty core has no remaining film.
How to use this calculator
- 01
Measure current roll outside diameter and confirm the core outside diameter.
- 02
Enter complete-film thickness and actual web width.
- 03
Add GSM when a weight balance is needed and review remaining material before allocating it to a job.
A calculation you can check
The example estimates the balance on a partly consumed reel using its current diameter and known film specification.
- Roll outer diameter
- 350 mm
- Core OUTER diameter
- 90 mm
- Film thickness
- 80 µm
- Web width
- 800 mm
- Film GSM
- 80 g/m²
π × (350² − 90²) ÷ (4 × 80) = 1,123.119374 m; × 0.8 = 898.4954989 m²Check the displayed formula and units against your quotation. Use measured GSM, net weight and actual layout dimensions where available. Default densities are planning assumptions, not certified material properties. Calculated cost does not certify strength, compatibility or safe loading.
Method, units and material assumptions ↗