When comparing or combining an area or volume it is important to measure the objects using the same units. Without converting the areas into the same unit, it might be difficult to tell, for example, ...

Units from the metric system can be used to describe the mass, volume or length of an object. Mass is measured in grams (g) and kilograms (kg). Volume is measured in millilitres (ml) and litres (l).

A metric prefix is a numerical multiplier that is placed before a basic unit of measure to indicate a specified multiple or fraction of that unit. The 20 recognized metric prefixes have been specified ...