An alternative method for calculating pressure generated by a liquid column is to relate it to the
pressure generated by an equivalent column of water, resulting in a pressure expressed in units of
water column (e.g. inches W.C.) which may then be converted into PSI or any other unit desired.
For our hypothetical 12-foot column of oil, we would begin this way by calculating the specific
gravity (i.e. how dense the oil is compared to water). With a stated weight density of 40 pounds
per cubic foot, the specific gravity calculation looks like this