What is density?

Density (Greek:\rho) is a physical quantity determined as the quotient of the mass m and the volume V of a body or chemical.

P = \frac{m}{V}

The same equation holds for the average density of any material in volume V containing mass m. It describes how much mass of a substance is contained on average per unit volume: the more significant that mass, the denser the body is said to be. It follows that the unit of measurement for it in the SI system is the kilogram per cubic meter (kg / m3).

p = \frac{dm}{dV}

If the density of a substance or body is equal at each point (i.e., equal in each part of the volume), it is said that the substance or body is homogeneous (in the context of considering density or mass).

Homogeneous denotes the homogeneity (uniformity) of a property within the observed object, system, set, area, etc. The term has a wide and varied application, in which its meaning varies from complete uniformity to a relatively high degree of similarity. The actual density of a homogeneous body is equal to its average density so that the previous, more straightforward equation can calculate it. Substances that are pure chemical elements or compounds are homogeneous in the part of the volume in the same conditions (pressure, temperature, etc.).

How to find the density

The first step in discovering density is determining the weight of a liquid, metal, or gas. For example, we will use cooking oil. A small cup of oil weighs 100 g (without a cup).

The second step is to find the volume of the substance. In our case, it will be 100 cm ^ 3.

Divide the weight by the volume. 100 g / 100 cm ^ 3

If you want, switch to the appropriate size you need.

1g / cm ^ 3 = 1 (1/1000 kg) / (1/1000000 m ^ 3) = 100 kg / m ^ 3

A quick way is to use our density calculator if you don’t already have time to calculate it yourself.


Density is not an invariant characteristic of a substance but depends primarily on temperature, which is valid for all substances in all states of matter. For a gaseous state, it strongly depends on the pressure prevailing in that gas. As a rule, the density of all substances decreases with increasing temperature. But this will not be the case if the thermal expansion of the substance is in some way mechanically prevented; for example, then in gases, the pressure will increase, and in solids, stress will occur. The most well-known deviation from the usual decrease in density with increasing temperature is the water anomaly.

Size closely related to density is specific volume. The relationship of specific volume to density is as follows:

V = \frac{1}{\rho}

The unit of measurement of specific volume is cubic meters per kilogram (m ^ 3 / kg). This quantity tells us how much volume a unit of mass of a substance occupies.

Osmium is the densest of all the elements at standard pressure and temperature; density is 22 610 kg / m3. The lowest known density is the density of interstellar space, which is from 10−25 to 10−15 kg / m3, the density of the Earth’s atmosphere at sea level is about 1.2 kg / m3, at a temperature of 0 ° C and a pressure of 101 325 Pa, the density is water ice 916.7 kg / m3, water 1 000 kg / m3, saltwater 1 030 kg / m3, silicon 2 330 kg / m3, aluminum 2 700 kg / m3, iron 7 870 kg / m3, mercury 13 546 kg / m3, gold 19 320 kg / m3, the density of the Sun’s core is 150,000 kg / m3 and atomic nuclei 2.3 × 1017 kg / m3.

Density formula

The density formula is as follows:

D =\frac{m}{v}


D – density;

m – mass; and

v – volume.

Changing the density when heated

As the volume of the body increases with heating, its density decreases. If we denote the density of a body at 0 ° C by ρ0 and the volume by V0, and the density at any temperature t by ρ.

Thermal stretching, thermal stretching, or thermal dilatation is the property of a chemical to change volume depending on temperature. When matter heats up, the particles begin to move with a greater average distance between them. Materials that shrink with increasing temperature are rare and only for specific temperatures. The degree of expansion of a material divided by the diameter of the temperature is called the coefficient of thermal expansion and generally varies with temperature. Thermal expansion must be taken into account in all steel structures.

For example, for bridges, installation of boilers, laying of rails and pipes. Bridges must be installed in such a way as to allow them to stretch freely. Therefore, bridges and boilers are attached to the foundation only on one side, while their free end can be moved.

Density of water (at 1 atm)

Temp. (°C)Density (kg/m3)

Density of Common Materials – Table

MaterialDensity (g/cm3)State of Matter
Hydrogen (at STP)0.00009gas
helium (at STP)0.000178gas
carbon monoxide (at STP)0.00125gas
nitrogen (at STP)0.001251gas
air (at STP)0.001293gas
carbon dioxide (at STP)0.001977gas
ethanol (grain alcohol)0.810liquid
water at 20°C0.998liquid
water at 4°C1.000liquid

Frequently Asked Questions

How to find volume with density and mass?

Density measures the mass in a specific volume of a substance or how much material is in a particular space. Density is constant for a substance at a given temperature because an increase in the mass of a sample increases the volume proportionally. Density is calculated by dividing the mass of a substance by the volume (density = mass/volume). If the density of a substance is known, the volume can be calculated by determining the mass of a sample.

How to calculate population density?

The calculation for population density is total population divided by land area.

How to calculate the density of water?

Calculate the density by dividing the mass by the volume.
Using the equation density = mass/volume, you can determine the density of water. Plug in the values of mass and volume you determined and solve.

Be sure to check out our Force Calculator!