Styles and Formulas
General Types Of Manufacture
 | Bottom Seal
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 | Side-Weld: Polyethylene sheeting is folded to form the bottom of the bag, which is then sealed at each side creating a neat trim package.
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 | Perforated Rolls: A continuous roll of seamless tubing is made into bottom-seal bags which is perforated at specified bag lengths for easy tear-off of individual bags.
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 | Back Seal: Polyethylene sheeting is folded and sealed along the back to form a tube; then it is bottom sealed
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 | Perforated Lip: A side-weld bag may have a perforated lip which is stapled to a cardboard header for easy tear-off.
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 | Wicketed Bag: A side-weld bag with two holes punched in the lip. A metal wicket is inserted in the lip holding the bags together allowing for individual bag removal.
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 | Flat Sheeting: Polyethylene sheeting cut to size, for general wrapping, lining or dividing layers. |
Special Styles
 | Flip-Top Bag: A side-weld bag, where the lip tucks in for automatic closing. |
 | Header Bag: A side-weld bag with a continuous seal along the width 2-3” below the fold creating a header on which the bag will hang. |
 | Door Knob Bag: A poly bag with 1 ½” hole or slit in the body of the bag just below the opening. |
 | Pocket Bag: A bag is sealed into pockets for multiple product unit packaging per bag. |
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Film Weight / Yield Conversion Formulas
The following formulas are described to help understand the relationship between film weight and film length. It is important to understand this relationship because the film user is interested in length to determine how many objects can be wrapped with a particular order of film. This is a question of yield. The distributor also is interested in length, for the same reasons as the end user. The manufacturer needs to be able to convert length to pounds to be able to order raw materials which are sold in pounds.
Step 1 — How Do You Figure Square Inches?
Square inches = opening (width) X length of any given piece of film.
For bags there are two sides and in many gussets, lips, back flips, etc. that need to be considered to determine total area. For film there are one (SWS) or two sides (tubing) and in many cases gussets or a lip.
Example A: Bag – 12” X 12” + 1 1/2 “ lip
13 ½” (side A = 12” + 1 ½”) + 12 (side B) = 25 ½
25 ½ X 12 (width) = 306 square inches per bag
Example B: Gusseted Bag – 14” (wide) X 12” (gusset) X 24” (length)
14” (width) + 12” (gusset) = 26”
26” X 2 (2 sides) = 52” X 24” (length) = 1248 sq. inches per bag
Example C: Film – 60” single wound sheet (SWS)
60” X 12” = 720 square inches per lineal foot
Example D: Film - 60” tube
60” X 2 (two sides) X 12” = 1440sq. inches per lineal foot
Example E: Film – 60” X 40” gusseted tube (40” gusset)
60” + 40” (gusset) = 100
100” X 12” X 2 (both sides) = 2400 square inches per lineal foot
Step 2 — How Do You Figure Weight?
Example A: Bag – 12” X 12” + 1 ½” lip X .002” (thickness)
13 ½” (side A face + lip) + 12” (side B face) = 25 ½”
25 ½” X 12” = 306” X .002 =.612
.612 ÷ 30 (constant factor) = .0204 pounds per bag
Example B: Bag – 14” X 12” X 24” X .00225 (thickness)
14” (side A face) + 14” (side B face) = 28”
12” (gusset A) + 12” (gusset B) = 24”
52” X 24” = 1248 X .00225 = 2.808
2.808 ÷ 30 (constant) = .0936 pounds per bag
Example C: Film – 60” X .0015 (thickness) SWS (single wound sheet)
60” X 12” (one lineal foot) = 720” X .0015 = 1.080
1.080 ÷ 30 (constant) = .036 pounds per lineal foot
Example D: Film – 60” tube X .00175 (thickness)
60” (side A face) + 60” (side B face) = 120”
120” X 12” (one lineal foot) = 1440” X .00175 = 2.520
2.520 ÷ 30 = .084 pounds per lineal foot
Example E: Gusseted Tube – 60” X 40” X .0007 (thickness)
60” (side A face) + 60” (side B face) = 120”
40” (gusset A) + 40” (gusset B) = 80”
120” + 80” = 200”
200” X 12” (one lineal foot) = 2400” X .0007 = 1680 ÷ 30 = .056 pounds per lineal foot