This document contains information about units of measurement in A-level Physics. It discusses: 1) The seven base SI units including kilogram, metre, and second. Units must be specified and written in the singular form. 2) Prefixes for units, such as milli, centi, and kilo, and converting between standard numerical forms. 3) Derived units that can be expressed as combinations of base units, like converting the newton to kg m/s^2. 4) Examples of converting between different units, such as centimeters to metres, and estimating typical physical quantities.