Density Calculator
Calculate density (density = mass / volume) given mass and volume.
Calculated Density
Mass, volume, and why things float
Density is mass divided by volume — how much matter occupies a given space. The SI unit is kg/m³, though g/cm³ is more convenient at human scale, and the two differ by a factor of exactly 1000. Water is the reference point worth memorising: 1 g/cm³, or 1000 kg/m³, which makes it easy to judge anything else at a glance.
Floating follows directly. An object less dense than the fluid around it floats; denser, it sinks. Steel is roughly 7.8 g/cm³ yet ships float, because a hull encloses a large volume of air and theaverage density of the vessel is what matters, not the density of the material. The same reasoning explains hot air balloons and why ice floats — water is unusual in expanding as it freezes, so ice is about 9% less dense than the liquid.
Two practical notes. Density changes with temperature, since most substances expand when heated, so precise figures are quoted at a stated temperature. And specific gravity is just density relative to water, which makes it dimensionless — a specific gravity of 2.7 means 2.7 times as dense as water, and it is the figure geology and brewing tend to use.
Frequently asked questions
What is density?
Density is the measure of mass per unit volume of a substance. Formula: density = mass / volume.
How do I convert between density units?
1 g/cm3 equals 1,000 kg/m3 and about 62.43 lb/ft3. Water at 4 C is almost exactly 1 g/cm3, which is what makes it the reference for specific gravity - a material with a specific gravity above 1 sinks in water and below 1 floats.
What units does this use?
You can use any consistent units (kg/m³, g/cm³, etc.) as long as mass and volume are in compatible units.
Is my data stored?
No. All calculations run locally in your browser.