LDPE liner weight calculator
A liner is its own article: its own lay-flat width, its own length and its own seal, in micron or gauge. Enter them here and get the weight of one liner, the kilograms an order needs and an indicative cost. Sizes in mm, cm or inch.
Liner specification
The formula is the one the Nexora engine uses for a liner: gauge = micron × 4, then weight = (gauge ÷ 3300) × width in inches × cut length in inches. The lay-flat width already accounts for the two layers of the tube, so do not double it. Plants differ in seal allowance and film tolerance, so treat this as a quotation check.
Real costing uses your own dated LDPE price and your plant's waste norms, and rolls the liner into the bag's own Bill of Materials.
How a liner's weight is calculated
A liner is a lay-flat polyethylene tube dropped inside a woven sack to keep moisture out. Because it is a tube, its lay-flat width already carries both layers of film, which is why the woven sack formula divides by 3300 rather than multiplying an area by a density twice.
cut length = finished length + bottom seal allowance
weight (g) = (gauge ÷ 3300) × (lay-flat width in inches) × (cut length in inches)
order kg = weight × quantity × (1 + waste %) ÷ 1000
The calculator also shows a cross-check worked the other way — lay-flat width × cut length × 2 layers × micron × 0.92 — so you can see the two agree within a couple of percent. Where they differ, the difference is the film tolerance your supplier actually delivers.
Typical liner specifications
- Cement and putty 25–50 kg: 40–60 micron (160–240 gauge), lay-flat width matching the sack, 5–8 cm bottom seal.
- Food grain and sugar: 50–75 micron, often with a gusset so the liner opens square inside the sack.
- Chemicals and fertiliser: 75–100 micron, sometimes co-extruded or with a moisture barrier layer.
FAQ
How do I convert liner micron to gauge?
Multiply by four. A 40 micron liner is 160 gauge; a 75 micron liner is 300 gauge. The calculator accepts either and shows both.
Should I double the width for the two layers?
No. Enter the lay-flat width as measured flat. The formula's divisor already accounts for the tube being two layers.
Why is the liner no longer in the bag calculator?
Because it is a separate article with its own width, length and seal, and it is often bought rather than made. Calculate it here and add it to the bag when you cost the order. In the desktop app the liner is one line of the bag's Bill of Materials.
What bottom seal allowance should I use?
Most plants allow 50–80 mm for the bottom seal. Use your own figure; the calculator adds it to the finished length to get the cut length.