Packaging Calculations

How to Calculate Film Yield, Web Speed, and Waste in Packaging Manufacturing

Work through the core packaging math: extrusion yield in linear feet per pound, converting output, adhesive coat weight, and roll capacity, all with real inputs.

Film extrusion yield is the anchor calculation. Yield in square inches per pound equals 30,000 divided by (density times mils), where density is in g/cc and mils is film gauge. For LDPE at 0.923 g/cc run at 2.0 mil, yield is 30,000 / (0.923 x 2.0) = 16,251 sq in per lb, or about 113 sq ft per lb. On a 24 inch wide web that converts to 56.4 linear feet per pound. The Film Extrusion Yield calculator handles blends and coextruded layers, but keep the constant straight: 30,000 assumes water density of 1.0 g/cc baseline.

Line output for bag converting comes from web speed and repeat length. Bags per minute equals (web speed in feet per minute times 12) divided by cutoff length in inches. A machine at 400 fpm cutting a 15 inch bag repeat makes (400 x 12) / 15 = 320 bags per minute, or 19,200 per hour at 100 percent uptime. Multiply by number of lanes for multi-up tooling: a 4 up head at that rate yields 76,800 pieces per hour. The Bag Converting Speed calculator lets you back-solve required fpm for a target daily count.

Lamination adhesive usage drives cost and cure. Dry coat weight in pounds per ream (3,000 sq ft) equals coat weight in grams per square meter times 0.614. A solventless laminate at 1.6 gsm equals 0.98 lb per ream. To convert to solids-adjusted wet demand, divide dry weight by the solids fraction: at 100 percent solids, wet equals dry; at 40 percent solids solvent-based, wet gallons climb 2.5 times for the same dry lay-down. The Lamination Adhesive Usage calculator ties gsm, web width, and run length into total kilograms per job.

Roll diameter tells you how much film fits before a splice or core change. Outer diameter in inches equals the square root of ((4 x length in inches x thickness in inches) / pi plus core OD squared). For 10,000 feet of 2 mil film on a 6 inch core: length is 120,000 in, thickness 0.002 in, so OD equals sqrt((4 x 120,000 x 0.002)/3.1416 + 36) = sqrt(305.6 + 36) = 18.5 inches. The Roll Diameter Capacity calculator inverts this to give footage from a target build diameter and gauge.

Label roll waste combines splice loss, core waste, and startup scrap. Usable labels per roll equals ((roll footage minus leader and trailer waste) times 12) divided by (label repeat plus gap). With a 5,000 ft roll, 40 ft total leader and trailer loss, a 4 inch label and 0.125 inch gap: ((5,000 minus 40) x 12) / 4.125 = 14,429 labels. That 40 ft loss is 0.8 percent scrap before any press defects. The Label Roll Waste calculator separates each waste bucket so you can attack the largest one first.

Print registration loss during changeover is web length, not time. Registration scrap in feet equals press speed in fpm times seconds to achieve register, divided by 60. A gravure line at 700 fpm taking 45 seconds to lock registration wastes 700 x 45 / 60 = 525 feet per color change. Across 8 colors that is 4,200 feet of setup scrap per job before the good run starts. The Print Registration Loss calculator multiplies this by material cost per foot so you see the dollar hit, not just the footage.

Case pack math closes the loop from web to pallet. Cases per pallet equals floor(pallet length / case length) times floor(pallet width / case width) times floor(usable stack height / case height). On a 48 by 40 inch pallet with 12 by 9 by 6 inch cases and 50 inch stack: 4 x 4 x 8 = 128 cases. Multiply by bags per case to get sellable units per pallet. The Case Pack Optimization calculator tests rotated orientations to raise cube utilization from a typical 68 percent toward 85 percent.

Published 2026-07-01.