Enter bag size and thickness to see how much each bag weighs, how many bags come from a pound of film and the cost per thousand; for rolls, see how many feet and pounds fit in a given diameter.
Pre-sizing and estimating tool: results do not replace design, calculations or reports signed by a licensed professional, nor verification against the applicable codes and standards.
Weight of one bag at the current size and cost per thousand, for several thicknesses. The dashed line is the current thickness.
Film length, net and gross weight and area of the roll entered.
Film length and net weight for outside diameters from the core up to 1.5 times the current one. The dashed line is the current diameter.
The calculation report gathers this page's inputs, results, equations, assumptions and references, with fields for project, engineer and revision. The full report also includes the charts and interpretations, in color. In the print dialog, choose Save as PDF.
Multiply the bag’s film area by thickness and resin density. A flat 16 × 24 in bag has two faces, or 768 in² of film; at 2 mil of LDPE (0.92 specific gravity) it weighs 0.817 oz. The shortcut is yield: 27,680 ÷ (0.92 × 2) = 15,043 in² per pound, and 768 ÷ 15,043 = 0.051 lb per bag.
Divide one pound by the bag weight. In the example, 1 ÷ 0.051 lb = 19.6 bags per pound, and 1,000 bags weigh 51.05 lb. To check a delivery, weigh 100 bags; blown film thickness usually varies ±10% to ±15%.
Multiply the weight of 1,000 bags by the price per pound. In the example, 51.05 lb at $1.50 per pound is $76.58 per thousand. Going from 2.0 to 1.8 mil would cut that by 10%, about $77 on a 10,000 bag order.
A mil is a thousandth of an inch (25.4 µm); 100 gauge equals 1 mil. Basis weight is the weight of one square yard or meter of a single ply. A gusset is the side or bottom fold that gives the bag volume; enter its open depth.
Length is the area of the ring of film (outer circle minus core) divided by the thickness of each wrap. A 16 in roll on a 3.5 in core with 2 mil flat film holds 7,977 ft; at 20 in wide it weighs 127.3 lb net. If the film is tubing, with 2 plies per wrap, the footage halves.
It assumes uniform thickness, seals with no added mass and no air between wraps. Films with calcium carbonate filler or white pigment are denser than the base resin; check the data sheet. Trim and seal waste is in the supplier’s price per pound.
Important notice: Indus Metrics tools produce estimates and pre-sizing results from the data you enter and from published engineering methods. They do not replace design, calculations or reports signed by a licensed professional engineer (PE), nor verification against the applicable codes, standards and regulations, such as OSHA rules and the ASME codes. Material and fuel properties vary: check manufacturer data or your own process analyses before deciding. By using this site you agree to the Terms of Use.
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