Traverse the chasm between volume and mass.
If you know the mass and the density, use the Volume tab. The answer is given in ml (or cm3)
If you know the volume and the density, use the Mass tab. The answer is given in grams
If you know the volume and the mass, use the Density tab. The answer is given in grams/ml
If you wonder what the density pre-populating the Density fields are, it is for Platinum.