Measurements of length, width and height are used to find the volume of a solid figure. Volume is measured in cubic units, because three values are being multiplied to arrive at the final figure.
Volume formulas differ depending on the shape of the object being measured. Cones, cylinders, spheres and pyramids are measured differently from each other and from cubes or rectangular solids.
To find the volume of a cube with sides 3 inches long, multiply the length times the width times the height, 3 x 3 x 3. This gives 27, so the volume is 27 inches cubed, or 27 cubic inches.