A physical quantity is something that can be measured. Scalar quantities only have a magnitude or size.

Examples of scalar quantities

Some examples of scalar quantities include:

• temperature, eg 10 degrees Celsius (°C)
• mass, eg 5 kilograms (kg)
• energy, eg 2,000 joules (J)
• distance, eg 19 metres (m)
• speed, eg 8 metres per second (m/s)
• density, eg 1,500 kilograms per metre cubed (kg/m³)

Learn more on scalar and vector quantities, contact and non-contact forces in this podcast

Listen to the full series on BBC Sounds.

Calculations involving scalar quantities

Adding scalars

The sum of scalar quantities can be found by adding their values together.

Example

Calculate the total mass of a 75 kg climber carrying a 15 kg backpack.

75 kg + 15 kg = 90 kg

Subtracting scalars

Scalar quantities can be subtracted by subtracting one value from another.

Example

A room is heated from 12°C to 21°C using a radiator. Calculate the increase in temperature.

21°C - 12°C = 9°C