SI Unit

The International System of Units (SI) is the globally accepted measurement standard used in science, engineering, and commerce. It ensures consistency and precision across all disciplines and industries.

SI Base Units

The SI system is built on seven fundamental units:

• Second (s): time

• Meter (m): length

• Kilogram (kg): mass

• Ampere (A): electric current

• Kelvin (K): thermodynamic temperature

• Mole (mol): amount of substance

• Candela (cd): luminous intensity

Derived Units

SI derived units are formed by algebraically combining base units:

• Newton (N): force = kg·m/s²

• Watt (W): power = kg·m²/s³

These units allow for consistent measurement of complex physical quantities.

Example

The speed of light is defined as exactly 299,792,458 meters per second, combining the base units for length and time.

2019 Revision

In 2019, all SI base units were redefined using fixed values of fundamental physical constants (e.g., Planck constant, Boltzmann constant). This revision improved long-term stability and global consistency of measurements.