This equation calculates the mass or weight of a substance from a conduit. This equation lets the user enter any interior diameter of circular conduit (diameter) and the linear speed of flow (speed), the duration of flow (duration) and it calculates the volume that has flowed through the conduit. It then multiplies the volume by the mean density of the substance to calculate the mass. Assuming normal gravity, the mass can be converted to weight. The default mean density is 1000 kg/m3 which is the mean density of fresh water.