How do I measure a Poly Bag?
When communicating the size of a simple plastic bag, the FIRST measurement listed is always the width across the open end, followed by the length from the opening to the bottom. If the bag has side gussets, the total length of the gusset (from outside edge to outside edge) is inserted between the width and length measurements. If the bag has a bottom gusset, the total length of the gusset 9from bottom edge to bottom edge) is inserted just after the length measurement.
Note on Gussets: Side gussets and bottom gussets are mutually exclusive....one cannot exist if the the other present. A side gusset is always smaller than the overall width of the bag. Side or bottom gussets are measured across the gusset when it is fully open.
Thickness: The final measurement that must be known to produce an accurate plastic bag quote is the thickness. All plastic film used by Custom Poly Packaging to produce poly bags is unsupported (conforms to objects, flexible) and has a thickness measured in thousandths of an inch (or "mils").
The flexible packaging "industry standard" is to manufacture plastic bags with an actual thickness of 10% less than the thickness requested by the customer. We refer to this lighter film gauge as a "nominal thickness". Thus, .002 (or 2 mil) nominal thickness is an actual measured thickness of .0018 (or 1.8 mil).
Note: Custom Poly Packaging expresses actual thickness measurements in its quotes rather than nominal measurements.
For competitive pricing when requesting a quote, please inform Custom Poly Packaging whether the thickness requested is the actual (full gauge) measurement or nominal.
Here are some examples of measurements for flexible packaging bags made by Custom Poly Packaging from unsupported Low Density Polyethylene (LDPE), High Density Polyethylene (HDPE) or Polypropylene (PP) films:
- Flat poly bag 12x18 .0018 = 12" wide across opening x 18" long with .0018" thick film (no gussets).
- Side-gusset poly bag 8x4x20 .00225" = 8" wide across opening with 4" side gusset when fully open by 20" long from opening to bottom and .00225" thick film.
- Bottom gusset poly bag 10x15x4 .0017" = 10" wide across opening by 15" long from opening to bottom with 4" bottom gusset when fully open and .0017" thick film.
These bag styles are always written in this manner. Note that the side gusset cannot be larger than the lay flat width and the bottom gusset cannot be bigger than the length.
Note about Zipper Bags: For zipper bags, the length measurement measures the distance from the zipper to the bottom of the bag. Unless the customer specifies otherwise, Custom Poly Packaging assumes a 1" lip above the zipper.
When requesting a quote on a new poly bag, having the dimensions of the bag or the dimensions of the item(s) that will be packaged will help facilitate the quoting process. Items to be packaged in a poly bag can have large variances in density. Unfortunately, to ask for a quote on a "12 oz" bag or "2 cubic foot" bag is not enough information to calculate the dimensions of the bag. We must know the physical measurements of the volume (width, diameter, length, height) to calculate the size of the bag required.
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