Well, technically yes but to determine the full capacity of the volume of all the pockets of our packs we use the "Standard Test Method for Measurement of Backpack Capacity". Allow us to explain.
Since backpacks are not completely rectangular or square, getting the volume by way of the method that is commonly used for shapes, Length x Width x Height does not work.
Also, this test method does not consider the areas of the backpack that are not entirely enclosed by fabric, such as mesh pockets, water bottle holders, and compressor pockets.
First we fill all the compartments with hollow in-compressible plastic spheres. We make sure the pack is completely filled and has no voids.
Once the bag is filled to the brim, the spheres are emptied into a large cylinder.
After all of the spheres have been removed from the pack and placed into the cylinder, a wooden disk referred to as a piston is placed inside. The top of the piston represents the packs extended volume in liters. We also convert the liters into cubic inches using the following formula:
Cubic Inches = Liters × 61.023744