What are all SI units

SI units

In this article we deal with the so-called SI units. We explain to you how important the SI units are in physics and give you a lot of examples for them. This article belongs to the Physics Basics section.

Do I put a distance in meters, centimeters or kilometers in a formula? The answer to this is provided by the international system of units, abbreviated to SI (from French: Système international d’unités) and is the system of units based on the international system of sizes (ISQ). The information in the SI unit is inserted into a physical formula. If a task text does not provide the SI unit, it must first be calculated and only then be used in the formula.


SI units of physics

In the international system of sizes and units, the seven basic sizes are expressed by the basic units meter (m), kilogram (kg), second (s), ampere (A), kelvin (K), mol (mol) and candela (cd) and defined in the SI in this order. In the following list you will find some important quantities that are regularly used in formulas.

  • Route / length: A distance is used in meters, for example 5 m.
  • Dimensions: A mass is used in kilograms, for example 8 kg.
  • time: The time is entered in seconds, for example 10 s.
  • electricity: The current strength is used in amperes, for example 20 A.
  • temperature: The temperature is given in Kelvin, for example 200 K.
  • Amount of substance: The amount of substance is given in moles, for example 10 mol.
  • Light intensity: The strength of the light is given in candela, for example 40 cd.


In the formula of the uniform movement, we insert the speed in meters per second, the time in seconds and the starting distance in meters and thus calculate the distance.


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