Roll Weight from Diameter Calculator
Estimate net roll weight by combining roll geometry with web width and GSM. First calculate length from diameter and thickness, then convert that length into film mass.
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.
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 net film weight
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.
Length = π × (OD² − core OD²) ÷ (4 × thickness); weight = length × width × GSM ÷ 1,000
π × (350² − 90²) ÷ (4 × 80) = 1,123.119374 m; 1,123.119374 × 0.8 × 80 ÷ 1,000 = 71.87963991 kgSaved 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 net film weight
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.
Diameter alone is not enough to determine film weight: the core, winding thickness, width and basis weight all matter. The geometric step estimates how much running length fits around the core. That length multiplied by width gives area, and GSM gives its net material mass. The separate thickness and GSM inputs let the calculation represent multilayer films without assuming one polymer density.
How to use this calculator
- 01
Enter measured roll OD and core OD with the total film thickness.
- 02
Enter web width and the average GSM of the complete structure.
- 03
Review net mass and distinguish it from gross roll handling weight.
A calculation you can check
The example estimates a reel’s net film mass from its physical diameter and the corresponding 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; 1,123.119374 × 0.8 × 80 ÷ 1,000 = 71.87963991 kgCheck 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 ↗