Formula For Density

Density Formula

Density is of an object or material is its mass per unit of volume. The symbol used for denoting density is the lower case Greek letter rho (ρ). The simple formula for calculating density is:

Density Formula where ρ (rho) is density, m is mass and V is volume.

In layman’s terms density is described as the weight per unit of volume, however this is technically incorrect as the quantity should be defined as specific weight. Specific weight is defined as the weight per unit volume of a material and more accurately fits with the density definition.

How do you measure the components needed to calculate density? As there are two components which are mass and volume you must know both variables to accurately calculate density.  Measuring mass can be done by using a set of scales or a balance. Measuring volume is harder and requires either geometric measuring of the object or via displacement of a fluid for a solid object. When you need to measure the volume of a fluid or gas you should use a hydrometer (used to measure the specific gravity of a fluid) or dasymeter (used for measuring the buoyant effect of gasses).

An example of a density calculation is as follows. Imagine that you have a large brick of compressed coffee measuring 20cm x 20cm x 5cm that weighs 852 grams, what would be the density of your coffee brick? With the two variables you can then go about calculating density via the density formula above.

The first step is calculating the volume for which the formula is length x width x thickness. In our example those figures are 20*20*5 which equals 2,000 cm3. The second step is calculating density which as we know is mass / Volume. In our example we know that the mass of our coffee brick is 852 grams and the Volume is 2,000 cm3.  852g / 2,000 cm3. = 0.426 g/cm3. The density of the coffee brick is 0.426 g/cm3.