How this calculation works
Start with one complete circumferential turn that supplies the initial film-width band. Use film width and overlap for helical pitch, add entered extra top and bottom turns, divide the traveled path by the length ratio and add original-film tails.
Original length = (one complete starting turn + helical path + extra stationary turns) / stretch ratio + unstretched tailA worked example
The example 1.2 × 1 m load has a 4.4 m perimeter. A 0.5 m film at 50% overlap advances 0.25 m per turn; a 1.5 m load needs four helical turns per pass after the initial band.
Good to know
Ideal rectangular path only, not a load-containment specification. Assumes no neck-down, puncture, machinery loss or roll core mass. Original thickness and density determine film mass.
Reference: OpenStax: Pythagorean path geometry (opens in a new tab) ↗
Define stretch as a length ratio
A ratio of two means two metres of stretched path use one metre of original film. This is a 100% increase over original length, not a 200% added-stretch convention.
The tail input is original unstretched film and is added after division. Mixing the two length bases would undercount or overcount material at every pallet.
Overlap determines helical pitch
Pitch is applied film width multiplied by one minus the overlap fraction. The first film-width band already covers the bottom region, so helical vertical travel starts after that initial band.
Each rising turn travels around the perimeter and advances vertically. Its idealized path uses the hypotenuse of those distances. One complete starting turn supplies the initial band once per pallet. Entered top and bottom turns are additional stationary circumferential paths; they do not replace that starting turn.
Mass uses original film dimensions
Multiply original length by original width, original thickness and material density. Do not also thin the film by the stretch ratio while using the already reduced original length; that would apply stretch twice.
Real wrapping changes width and thickness and depends on equipment and load shape. This page explicitly assumes applied width equals original width and makes no claim about required containment force.
Use the result with the next measurement
The packaging dunnage volume and purchase calculator estimates internal carton void fill. Outer pallet wrapping and internal cushioning use different geometric and protection assumptions.
Ideal rectangular path only, not a load-containment specification. Assumes no neck-down, puncture, machinery loss or roll core mass. Original thickness and density determine film mass.
A few questions, answered
Does ratio two mean 200% added stretch?
No, it means stretched length is twice original length.
Are tails stretched in the calculation?
No, they are entered original-film lengths.
Does the result certify load security?
No, it estimates material under stated geometry only.