Constants & Units · constant

Speed of light in vacuum

c = 299 792 458 m s⁻¹

Unit: m s⁻¹
Value: 299 792 458
Exact: yes
Note: Fixes the metre. The universal speed limit and the conversion factor between space and time.
Symbol: c
Category: Defining (SI)
Numeric: 299792458
Uncertainty: exact

Equations

Schwarzschild Radius Fine-Structure Constant Klein–Gordon Equation Lorentz Factor Ampère–Maxwell Law Mass–Energy Equivalence Einstein Field Equations Chandrasekhar Limit Lorentz Transformations Gravitational Time Dilation Planck's Law FLRW Metric

Referenced by

equation

Ampère–Maxwell Law Chandrasekhar Limit Einstein Field Equations FLRW Metric Fine-Structure Constant Gravitational Time Dilation Klein–Gordon Equation Lorentz Factor Lorentz Transformations Mass–Energy Equivalence Planck's Law Schwarzschild Radius

Open on the Constants & Units shelf — the interactive card, the filters, and everything alongside it.

From the Constants database in Notion, last edited 2026-08-15. This page is the row, rendered by the build; nothing on it is written by hand.