What is the formula for density?

Density equals mass divided by volume: rho = m / V. To find mass, rearrange to m = rho x V. To find volume, use V = m / rho. Density is measured in kilograms per cubic metre (kg/m3) in SI units, or grams per cubic centimetre (g/cm3) in the cgs system, where 1 g/cm3 = 1000 kg/m3.

What is the density of water?

Pure water at 4 degrees Celsius has a density of exactly 1.000 g/cm3 (1000 kg/m3). This was historically used to define the kilogram. At room temperature (20 C), water density is approximately 0.998 g/cm3. Seawater is denser, around 1.025 g/cm3, due to dissolved salts.

How do you find the density of an irregular object?

Measure the object's mass on a scale. Then find its volume by water displacement: submerge it in a measuring cylinder of water and record the rise in water level. The volume of the object equals the volume of water displaced. Divide mass by volume to get density. This is Archimedes' principle.

Density Calculator

This calculator solves the density equation, rho = m / V, for any one of the three variables when you know the other two. Density is a measure of how much mass is packed into a given volume, and it is one of the most fundamental physical properties used to identify materials, design structures, and understand buoyancy. You choose what you want to find, enter the two known values, and the calculator returns the result with unit conversions. When solving for density, you enter mass in grams and volume in cubic centimetres, and the result is returned in g/cm cubed and kg/m cubed. When solving for mass, you enter density in g/cm cubed and volume in cm cubed. When solving for volume, you enter density in g/cm cubed and mass in grams. The calculator also shows density in kg per litre, which is numerically the same as g/cm cubed and convenient for liquids. A relative density (specific gravity) figure is shown relative to water at 1.0 g/cm cubed, indicating whether the object would sink or float. This tool is useful for chemistry students, materials engineers, geologists identifying rock or mineral samples, and anyone needing to convert between mass, volume, and density. Note that density varies with temperature and pressure; the results here are for a uniform material at constant conditions.

Solve for

Mass (m)

Volume (V)

cm³

Density (ρ)

g/cm³

2.50 g/cm³

density

kg/m³2500

kg/L2.50

Specific gravity2.50

Floats in water?No (sinks)

How it works

The three rearrangements of the density equation are: ρ = m / V (density), m = ρ × V (mass), and V = m / ρ (volume). The default inputs are in grams and cubic centimetres, giving density in g/cm³. To convert to kg/m³, multiply g/cm³ by 1,000. kg/L is numerically identical to g/cm³. Specific gravity is density relative to water (1.0 g/cm³); values below 1.0 float in fresh water.

Worked example

A sample has a mass of 500 g and a volume of 200 cm³. Density = 500 / 200 = 2.50 g/cm³ = 2,500 kg/m³. Specific gravity is 2.50, so the material is 2.5 times denser than water and will sink. This is close to the density of aluminium (2.70 g/cm³). These match the defaults above.

Related calculators

Percent Error Calculator: compare your measured density against a known reference value.
Force Calculator: find the weight force of the object once you know its mass.
Potential Energy Calculator: use the mass found here to calculate stored gravitational energy.
Specific Heat Calculator: another thermophysical property that characterises materials.

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