How tightly matter is packed
Density measures how much mass is squeezed into a given volume. It is why a small lead ball feels heavy while a large foam block feels light, and why some things float while others sink. This calculator relates density, mass, and volume so you can find whichever one you are missing.
How to use the calculator
Enter any two of density, mass, and volume, leaving the third blank. Density is in kilograms per cubic metre (kg/m³), mass in kilograms, and volume in cubic metres.
The formula
ρ = m ÷ V. Rearranged, mass = density × volume and volume = mass ÷ density. Water is the standard reference at 1,000 kg/m³, which is a handy anchor: substances denser than water sink in it, and less dense ones float.
Floating, sinking and everyday density
Oak wood (about 700 kg/m³) floats, steel (about 7,800 kg/m³) sinks, and air is roughly 1.2 kg/m³. So how does a steel ship float? Its average density — the total mass divided by the whole hull volume, most of which is air — is less than water, so it stays up. The same principle explains hot-air balloons (heated air is less dense than the cooler air around it) and why ice floats on water, an unusual property that keeps lakes from freezing solid from the bottom up.