Density Calculator
Calculate density, mass, or volume given the other two. Uses the formula D = M ÷ V.
Density calculations come up in materials science, engineering, cooking, and construction. Knowing that concrete has a density of about 2.3 g/cm³ lets you calculate how much a slab weighs. Knowing that gold is 19.3 g/cm³ and lead is 11.3 g/cm³ explains why a gold coin is noticeably heavier than a same-sized lead coin.
Water's density is exactly 1 g/cm³ at 4°C, this is intentional. The gram was originally defined as the mass of 1 cm³ of water. Materials denser than water sink; materials less dense than water float.
What density measures
Density is mass per unit volume, how much matter is packed into a given space. High-density materials have more mass in the same volume. Iron is about 7.87 g/cm³, a 1 cm³ cube of iron weighs 7.87 grams. A 1 cm³ cube of water weighs 1 gram. A 1 cm³ bubble of air weighs about 0.0012 grams. The same volume, dramatically different masses.
Archimedes and buoyancy
An object floats if its average density is less than the fluid it's in. A steel ship floats despite steel being denser than water because the ship's total volume (including the hollow interior) gives it an average density less than water. A solid steel ball sinks because its average density is 7.87 g/cm³, far above water's 1 g/cm³. This is Archimedes' principle: a submerged object displaces fluid equal to its volume, and if the displaced fluid weighs more than the object, it floats.
Density in everyday contexts
Density matters for shipping (heavier goods cost more to transport by weight, but bulky light goods may hit volume limits first), cooking (a cup of flour is less dense than a cup of sugar, important for baking precision), construction (calculating the weight of materials), and materials selection (choosing between aluminum and steel involves trading density for strength).
Frequently asked questions
Why does ice float on water?
Water is unusual, it's denser in liquid form than solid form. Most materials contract and become denser when they freeze. Water expands when it freezes, making ice (0.92 g/cm³) less dense than liquid water (1.00 g/cm³). This is why ice floats and why lakes freeze from the top down rather than the bottom up, critical for aquatic life in cold climates.
What is specific gravity?
Specific gravity is the ratio of a material's density to the density of water. Since water is 1 g/cm³, specific gravity numerically equals density in g/cm³ but is dimensionless. Gold has a specific gravity of 19.32, it's 19.32 times denser than water. Used extensively in geology, winemaking, and industrial applications.