Linear feet and regular feet are two ways of expressing the same exact unit of measurement. The reason that the word linear is occasionally used is to clarify that the unit of measurement is not being squared or cubed. Whenever you calculate the storage space of a given area, you are essentially calculating the volume of the space. Because the measurement of volume is always expressed in units cubed, you can never express an amount of storage space in terms of linear feet. Linear feet do play a vital role, however, in determining the cubed footage of an area.
Things You'll Need
 Tape measure

Measure the length of the storage space in linear feet.

Measure the width of the storage space in linear feet.

Measure the height of the storage space in linear feet.

Multiply the three measurements together. For example, if the length of the area is 10 feet, the width of the area is 5 feet and the height of the area is 8 feet, multiply 10 x 5 x 8 to give you 400. This resulting number is the amount of storage space expressed in cubic feet.
Tips & Warnings
 This method assumes that the storage space is the standard cube or cuboid shape.