What is density?
Density (ρ) is the mass of a substance per unit of volume, defined by the formula ρ = m / V. The SI unit is kilograms per cubic metre (kg/m³), though grams per cubic centimetre (g/cm³) is equally common in chemistry. Density determines whether an object floats or sinks: anything less dense than the surrounding fluid rises, while anything denser sinks. Water has a density of roughly 1 000 kg/m³ (1 g/cm³), making it the everyday benchmark.
How to use this calculator
Choose what you want to find—Density, Mass, or Volume—with the toggle. Enter the two known values and click Calculate. The result card shows the answer, the applied formula, and a plain-language interpretation that tells you whether the material is denser or less dense than water. When solving for density, a full set of unit conversions (kg/m³, g/cm³, kg/L, lb/ft³, and more) appears automatically. A reference grid of common material densities sits below the calculator for quick look-up.
Rearranging the formula
From ρ = m / V you can derive m = ρ × V (find mass) and V = m / ρ (find volume). The calculator handles the rearrangement for you—just pick the unknown and enter the other two values.
Practical applications
Engineers select materials by density when weight matters—aluminium (2 700 kg/m³) is favoured over steel (7 850 kg/m³) in aircraft. Geologists identify minerals by their characteristic densities. Brewers and winemakers measure liquid density to track fermentation. Shipping companies calculate cargo weight from volume and density. Quality-control teams verify that manufactured parts meet density specifications, catching voids or contamination.
Tips
Use consistent units—kg with m³, or grams with cm³. Temperature affects density: warm fluids expand and become less dense. For irregular objects, measure volume by water displacement. This free calculator runs entirely in your browser with no sign-up, no download, and instant results on any device. Bookmark it for quick density calculations whenever you need them.