Film Roll Length Calculator
Estimate film length on a roll from outer diameter, core diameter and film thickness.
Inputs
mm
mm
µm
Results
- Estimated film length
- ≈ 3,564 m
- Estimated film length
- ≈ 11,693 ft
- Wound layer thickness
- 174 mm
⚠ Real rolls contain air between layers and wind tension varies, so actual length is usually somewhat lower.
Formula
Length (m) = π × (OD² − Core²) ÷ (4 × Thickness)
with OD and Core in mm and Thickness in µm (mm² ÷ µm = m)
Assumptions & limits
- Ideal winding: perfectly tight layers, no air entrapment, uniform thickness.
- Core diameter means the outer diameter of the core where the film starts.
- For double-wound or folded film, use the thickness of the full wound ply.
Worked example
π × (500² − 152²) ÷ (4 × 50) = π × 226,896 ÷ 200 ≈ 3,564 m.