Density is a fundamental physical property of matter that describes how tightly packed the mass of an object is within the space it occupies. It represents the ratio of mass to volume. Different materials have unique densities due to their atomic weights and structure, which explains why a small brick of gold weighs significantly more than a piece of wood of the exact same size.
The mathematical equation for density is expressed as: Density = Mass / Volume.
To solve this equation, you must measure two properties: - Mass (m): The amount of matter in the object, typically measured in grams (g) or kilograms (kg). - Volume (v): The amount of three-dimensional space the object occupies, measured in cubic centimeters (cm³) or liters (L).
For calculating mass when density and volume are already known, visit our material mass solver. To change measurement units before calculation, see our translating measuring units tool.
Density plays a vital role in determining buoyancy—whether an object will float or sink in a fluid. An object floats if its overall density is less than the density of the fluid. For example, wood floats in water because its density is less than 1.0 g/cm³, while steel sinks because its density is 7.8 g/cm³.
However, steel ships can float because their shape encloses a large volume of air, lowering the average density of the entire vessel. You can calculate the weight force exerted by these masses using our mass to weight force calculator. For checking basic division steps, use our everyday daily math helper.
Density is not always a constant value; it can change based on environmental conditions. Temperature is a primary factor: as substances heat up, their atoms vibrate more and expand, increasing volume and lowering density.
Water is a unique exception to the general temperature rule. While most liquids become denser as they cool, water reaches its maximum density at 4 degrees Celsius. As it freezes into ice, it expands and becomes less dense, which is why ice floats in water and lakes freeze from the top down.
Pressure is another factor, particularly in gases, where compression reduces volume and increases density. To round resulting density decimals to clean significant digits, refer to our decimal rounding utility.
Example 1: Suppose a solid block of aluminum has a mass of 270 grams and a volume of 100 cubic centimeters.
To find its density, divide mass by volume: 270 g / 100 cm³ = 2.7 g/cm³. The density of aluminum is exactly 2.7 grams per cubic centimeter.
Example 2: Suppose you have an unknown liquid with a mass of 800 grams filling a container with a volume of 1,000 milliliters.
Divide mass by volume: 800 g / 1,000 mL = 0.8 g/mL. Since the liquid's density (0.8 g/mL) is less than that of fresh water (1.0 g/mL), it will float on top of water, helping you identify its physical properties.