Work out web tension instantly with clear inputs, formula shown and shareable results.
Web tension is specified per unit width so it scales with the material, not the machine: total tension is tension per millimetre x web width. Dividing by the cross-section gives stress, and stress over modulus gives the elastic stretch, which must stay well below yield to avoid permanent elongation and registration drift.
Web tension
Total tension (N) = tension per mm width x web width (mm)
Stress and strain
Stress = tension / (width x thickness); strain % = stress x 100 / modulus
Typically 10-25% of the material's yield strength expressed per unit width — around 0.3-0.9 N/mm for common packaging films and 1-3 N/mm for paperboard. Always check the supplier's data sheet.
Too high stretches the web, causes registration errors, telescoping rolls and web breaks. Too low causes wrinkles, wander, poor winding and slack loops at splices.