Enter your bag size and thickness to see the weight per bag, bags per kilo, the total weight of an order and what it means for the Plastic Packaging Tax.
Assumes a standard two-layer bag (front and back) plus a single-layer lip, in polyethylene at 0.92 g/cm³. Real weights vary by a few per cent with film type and seals.
* At the UK rate of £228.82 per tonne from 1 April 2026. Only businesses that manufacture or import 10 tonnes or more of plastic packaging in 12 months must register and pay. Not tax advice.
A mailing bag is made from one strip of film folded into a front and a back, with a lip that carries the adhesive strip. Its weight is the film area multiplied by the thickness and the density of polyethylene:
weight (g) = width × (2 × length + lip) × thickness × 0.92, with sizes in centimetres and thickness in centimetres (1 micron = 0.0001 cm).
For example, a 10 × 14″ bag (255 × 355 mm) with a 40 mm lip in 60 micron film weighs around 10.6 g. That is roughly 94 bags per kilogram, or about 10.6 kg per 1,000 bags.
Not sure which thickness you need? See our micron and gauge guide or use the size and gauge converter.
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