Now, we need to convert the capacity from gallons to cubic inches, as this is the standard unit for measuring volume. There are 231 cubic inches in a US gallon. So, to calculate the volume of the 55-gallon drum in cubic inches, we can multiply the capacity of the drum in gallons by the number of cubic inches per gallon.
Volume = 55 gallons × 231 cubic inches/gallon
Volume = 12,655 cubic inches
Therefore, the volume of a 55-gallon drum is 12,655 cubic inches.