For brands utilizing modern flexible packaging, like the custom digitally printed pouches offered by ePac Packaging, precision is everything. You need to know exactly how much product your pouch will hold to avoid costly under-filling, which can look unprofessional, or over-filling, which leads to material waste.
Fortunately, calculating the usable volume of the most common flexible pouch formats is straightforward once you understand their geometry.
Understanding the Different Pouch Types
The formula you use depends on the structure of your pouch. The main types of flexible pouches are:
| Pouch Type | Description | Key Feature |
|---|---|---|
| 1. Flat Pouch | Simple two-dimensional pouch, sealed on three or four sides. Lays flat when filled. | No depth or gusset (very minimal volume capacity). |
| 2. Stand-Up Pouch (SUP) | Features a bottom fold (gusset) that expands to allow the pouch to stand upright. Varies by bottom seal style. | Single bottom gusset provides depth. |
| 3. Flat Bottom Pouch | Features four vertical corners and a completely flat, rectangular base (often called a “quad-seal” or “side gusseted” pouch). | Gussets on both the sides and the bottom for maximum, box-like volume. |
How to Calculate the Volume by Pouch Type
To calculate the usable volume (V), you must measure the internal, fillable area of the pouch, which means measuring up to the zipper or seal line, not the very top edge.
1. Stand Up Pouch (SUP)
The Stand-Up Pouch is treated as a rectangular prism. The bottom gusset provides the depth dimension.
Key Dimensions:
- W (Width): Across the face of the pouch.
- H (Usable Height): From the base of the gusset up to the seal line/zipper.
- D (Depth/Gusset): The width of the flat bottom panel when the pouch is fully opened.
Volume (V)≈W×H×D
Example: A Stand-Up Pouch with a 15 cm width, 20 cm usable height, and a 6 cm gusset depth would have a nominal volume of:
V=15 cm×20 cm×6 cm=1,800 cm3
2. Lay Flat Pouch
Since a flat pouch has no gusset, its capacity is minimal and is generally used for very flat items, single-servings, or small amounts of powders/liquids that create a slight “pillow” shape when sealed.
Key Dimensions:
- W (Width): Across the pouch.
- H (Height): From the bottom seal to the top seal line.
- Note: This calculation provides the surface area, not the true 3D volume, which is difficult to calculate precisely for a pillow shape.
Area≈W×H
3. Flat Bottom Pouch
This style offers the largest volume for its footprint, as both the bottom and sides expand to form a stable box shape. Its volume calculation is more complex than the simple SUP. A common approximation involves adding the volume of the main body to the volume created by the side gussets.
Key Dimensions:
- W (Width): Across the front face.
- H (Usable Height): Up to the seal line/zipper.
- Dbottom (Bottom Depth): The width of the flat bottom panel.
- Dside (Side Gusset Depth): The width of one side panel when fully expanded.
A practical approximation often used is:
Volume (V)≈Wface×Husable×Dbottom
However, for a more accurate formula accounting for the box shape:
V≈(W×Dside×H)+(Dbottom×Dside×H)
(This combines the front/back panels and the side gussets to get the total volume).
Pro Tip For Accuracy
For products that are irregular, airy (like granola), or dense, the only truly accurate method is empirical testing:
- Fill Test: Fill an empty sample pouch with your actual product to the desired level.
- Transfer & Measure: Carefully empty the contents of the pouch into a volumetric measuring container (like a beaker or measuring cup) to determine the cm3 or Liter capacity.
This step is crucial because the density and bulk of your product will always affect the true fill capacity of any flexible pouch. By calculating your volume correctly, you ensure your ePac pouch—designed to maximize shelf presence—is also perfectly functional and efficient for your product!