Volumes of natural stockpiles: 1 ft 3 = m 3 = dm 3 = yd 3; 1 ft (foot) = m = 12 in = yd; stockpiling dumping angles; Mass of a Pile. The mass of a pile can be calculated as. m = ρ V (1) where . m = mass (kg, lb) ρ = density of the volume in the pile (kg/m 3, lb/ft 3) V = stockpiled volume (m 3, ft 3)