Original: With somewhat oblong diameters of 350–500 km, and a mass estimated to be 2.9% of the total mass of the belt,"Mass of 10 Hygiea" 0.445 / "Mass of Mbelt" 15 = 0.0296 it is the fourth largest object in the region by volume and mass.
Simplified: 10 Hygiea is the fourth biggest object in the asteroid belt, somewhat non-spherical with diameters of 350 – 500 km and a mass estimated to be 3% of the total mass of the asteroid belt.