When converting fluid measurements, which of the following is not a common unit?

When considering common units used in fluid measurements, the focus is typically on those that relate directly to the volume of liquids. Gallons, cubic feet, and cubic meters are all standard units for measuring volume. Gallons are widely used, especially in the United States, to quantify liquid capacities. Cubic feet and cubic meters are also fundamental units in both imperial and metric systems, respectively, to determine volume.

Pound per square inch (psi), on the other hand, measures pressure, not volume. It quantifies the force exerted by a fluid over a specific area and is typically used in contexts involving pressure in hydraulic systems, tires, and other applications dealing with gas or liquid pressures. Since the question specifically asks for a unit that is not common in liquid volume measurements, psi stands out as it pertains to a different physical property. This distinction clarifies why it is not considered a standard unit for fluid volume measurement.