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Polyethylene Bag Film Weight, Gauge and Cost per 1000 Calculator

Film is sold by the kilogram but bags are sold by the thousand. This calculator bridges the two using bag size, thickness and density, so you can quote or check a bag price quickly.

Your numbers

Bag width (lay-flat)

Bag length

Seal and fold allowance

Extra length used by the bottom seal and trim.

Film thickness

50 microns

Microns. One mil is 25.4 microns.

Film density

Film price

per kg

Resin plus extrusion cost, or purchased film price.

Converting scrap

Your results

Film weight per bag

13.4909

Grams including scrap.

Film cost per 1000 bags

$30

Film yield

21.7391

Square metres per kilogram at this gauge.

Film area per bag

0.282

Square metres, two layers of lay-flat film.

Bags per kilogram

Planning estimate for flat bags from lay-flat film. Gussets, handles and printing add material and cost.

Save results:

Cost per 1000 bags vs film thickness

Sweeps Film thickness from 15 to 150, holding your other inputs fixed.

Film costing in your ERP

Optional review of how to model film weight, yield and scrap in BOMs and standard costs.

Optional. The tool and every export work without this. No spam.

How to use it

Enter the lay-flat width and length of the bag and an allowance for the seal. Choose a thickness in microns and a density. Add your film price and scrap rate. The calculator gives film area per bag, grams per bag, bags per kilogram and film cost per 1000 bags. Move the thickness slider to see how cost responds. Cost is nearly linear in gauge, so a small thickness reduction saves a predictable amount.

The formulas

A bag made from lay-flat film uses two layers, so area per bag is 2 x width x (length + seal allowance). Because one micron of film over one square metre equals one cubic centimetre, grams equal area in square metres x thickness in microns x density in grams per cubic centimetre. Yield per kilogram is 1000 / (thickness x density). Cost per 1000 bags is grams per bag times price per kilogram.

Area = 2 x width x (length + seal)
Grams = area x microns x density
Bags per kg = 1000 / grams per bag
Cost per 1000 = grams per bag x price per kg

Common mistakes

Confusing mils and microns is frequent: 2 mil is about 51 microns. Another is forgetting that width in the bag spec may be a tube circumference or an open width rather than lay-flat width. Customers also quote gauge as nominal, while actual average thickness can be a few percent either side. Add a scrap allowance and a thickness tolerance in the quote.

1 mil = 25.4 microns
Use lay-flat width, not tube circumference
Add printing and additives to the price per kg
Check the tolerance on film thickness

Frequently Asked Questions

How do I convert mils to microns?

Multiply mils by 25.4. A 2 mil film is about 51 microns and a 3 mil film about 76 microns. Gauge is sometimes quoted in hundredths of a mil, so check the spec.

Why is area doubled?

A bag has a front and back panel made from the two sides of lay-flat film. Each panel is width times length, so total film area is twice that figure plus the seal allowance.

What density should I use?

LDPE and LLDPE are near 0.92 g/cm3, HDPE near 0.95 and PP near 0.91. Masterbatch and fillers shift this slightly. Use the data sheet for your resin.

Does this include printing cost?

No. It covers film only. Add ink, plates, set-up and conversion costs on top to get a full selling price.

If you want film weight and standard cost to flow into BOMs and quotes, we can help set that up in your ERP.

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