The volume \( V \) of a cube can be calculated using the formula:
\[ V = s^3 \]
where \( s \) is the length of one edge of the cube.
Given that the edge length \( s = 2.5 \) ft, we can calculate the volume as follows:
\[ V = (2.5)^3 = 2.5 \times 2.5 \times 2.5 = 15.625 \text{ ft}^3 \]
To express this result rounded to the nearest thousandth, we have:
\[ V \approx 15.625 \text{ ft}^3 \]
Therefore, the volume of the cube is 15.625 ft³.