Metal drums are common containers used to ship oil and many other materials. A metal drum is essentially a cylinder. A simple formula can allow you to calculate the volume of a cylinder from a few simple measurements.
Measure the height of the drum in inches. For example, a drum might measure 36 inches high.
Measure the diameter of the drum. This is the distance across a circular end. For example, the diameter might measure 18 inches.
Divide the diameter in half. This gives you the radius. For example, half of 18 inches is 9 inches.
Square the radius. Multiply the radius figure by itself to square it. For example, 9 inches squared is 81 inches.
Multiply the radius squared times pi times the height of the drum. Pi is approximately 3.14159265. The final result is the volume of the drum in cubic units, the same units you used to make the measurements. For example, calculate the radius squared (81 inches) times pi, then times the height (36 inches). The result is approximately 9,160 cubic inches.