Density Calculator
Density from mass and volume, with the sink-or-float check against water.
The formula and the anchor value
ρ = m / V
Water is the anchor: 1,000 kg/m³, which is 1 g/cm³ and 1 kg per liter. Anything with relative density above 1 sinks. Aluminium is 2.7, steel 7.9, gold 19.3, air about 0.0012.
Archimedes in one line
Density is how you identify a material without damaging it: weigh it, dunk it, divide. The displaced water gives the volume, and a crown that reads 15 instead of 19.3 has been cut with silver. Same trick, twenty-three centuries old.