# What units of measurement do scientists use?

##### 1 Answer

Practically all scientists use the **International System of Units** (**SI**, from the French *Le Système International d'Unités*).

#### Explanation:

**Base Units**

The SI is a system based around seven base units, each with their own symbols:

**metre (m)**: length

**kilogram (kg)**: mass

**second (s)**: time

**ampere (A)**: electric current

**candela (cd)**: luminous intensity

**mole (mol)**: amount of substance

**kelvin (K)**: temperature

**Derived units**

Derived units are formed by various combinations of the base units.

For example, velocity is defined as distance per unit of time, which in SI has the dimensions of metres per second (m/s).

Some of these derived units have special names and symbols:

**hertz (Hz)** — frequency (

**newton (N)** — force (

**pascal (Pa)** — pressure (

**joule (J)** — energy (

**watt (W)** — power (

**Multiplying Prefixes**

SI multiplying prefixes are used to form decimal multiples and submultiples of SI units.

There are prefixes for multipliers ranging from

The prefixes for the most common powers of ten are:

Thus, instead of writing a measurement as