Define the purchasing question
Empty envelope volume and dispensed cushioning quantity are related but are not interchangeable. A filler cost needs actual dosage and usable product yield.
Use void volume to explore geometry. Use measured dosage for filler cost and verify that right-sizing preserves protection before comparing complete systems.
Collect measurements that match the calculation
Measure internal carton size and the packed product envelope. For costing, measure the dispensed filler used by the qualified process and the usable yield per purchased pack in the same material state.
Check that one rectangular envelope fits in an orthogonal orientation, then subtract its volume. This free volume is not a filler dosage or a protection specification.
- Internal box length (mm)
- Internal box width (mm)
- Internal box height (mm)
- Product envelope length (mm)
- Product envelope width (mm)
- Product envelope height (mm)
Work through an illustrative case
Geometric free volume = Internal box volume − Product envelope volume
A 24 L internal box minus a 9 L envelope leaves 15 L geometric free space.
Replace these illustrative inputs with measured data or a quotation for the same scope. Change one assumption at a time so that a difference can be traced to a dimension, quantity, charge or process change.
Avoid the expensive comparison error
A product envelope may include empty spaces of its own. Compressed bag volume, inflated film volume and loose-fill volume cannot be substituted without a consistent measurement basis.
- Envelope volume can include internal product voids.
- Free volume does not establish a required cushioning quantity.
Common questions
What should I verify before using this result?
Measure internal carton size and the packed product envelope. For costing, measure the dispensed filler used by the qualified process and the usable yield per purchased pack in the same material state.
Does this calculation approve the packaging?
No. It estimates only the stated quantity, conversion or cost boundary. Technical performance and any required test or supplier approval remain separate.