The metric unit for measuring mass is the kilogram, abbreviated as $kg$.

In the metric system, mass is primarily quantified in kilograms. The kilogram serves as the base unit of mass in the International System of Units (SI). Its definition is based on the mass of the International Prototype of the Kilogram, which is a cylinder made of a platinum-iridium alloy and is kept in France. In everyday situations, we also frequently encounter smaller units such as grams ($g$) and milligrams ($mg$). Specifically, one kilogram is equivalent to $1,000$ grams, and one gram is equal to $1,000$ milligrams.

For larger masses, the metric system includes the tonne, abbreviated as $t$, where one tonne is equal to $1,000$ kilograms. This unit is commonly used in industries such as shipping and construction, where large volumes of material are handled.

In scientific applications, accurate measurements are crucial, and the metric system’s base-10 structure simplifies conversions between units. For instance, converting grams to kilograms involves dividing by $1,000$, and converting milligrams to grams also requires division by $1,000$.

A solid understanding of these units and the methods for converting between them is essential for tackling problems in GCSE Maths, particularly in areas such as density, where mass and volume are interconnected. The metric system is designed to be intuitive and logical, facilitating learning and application across various mathematical and scientific fields.