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Gravitational Constant (G) ❍｜Definition｜1st｜20251119205401-00-⌔

Gravitational constant - Wikipedia

Gravitational constant

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The gravitational constant is an empirical physical constant that gives the strength of the gravitational field induced by a mass. It is involved in the calculation of gravitational effects in Isaac Newton’s law of universal gravitation and in Albert Einstein’s theory of general relativity. It is also known as the universal gravitational constant, the Newtonian constant of gravitation, or the Cavendish gravitational constant,¹ denoted by the capital letter G. It is contrastable with (and mathematically relatable to) the Einstein gravitational constant, denoted by lowercase kappa (κ).

In Newton’s law, it is the proportionality constant connecting the gravitational force between two bodies with the product of their masses and the inverse square of their distance. In the Einstein field equations, it quantifies the relation between the geometry of spacetime and the stress–energy tensor.

The measured value of the constant is known with some certainty to four significant digits. In SI units, its value is approximately 6.6743 × 10${}^{-11}$ m${}^3$ ⋅kg${}^{-1}$ ⋅s${}^{-2}$.[

The modern notation of Newton’s law involving G was introduced in the 1890s by C. V. Boys. The first implicit measurement with an accuracy within about 1% is attributed to Henry Cavendish in a 1798 experiment.²

Printed 2026-06-28.

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Footnotes

1. “Newtonian constant of gravitation” is the name introduced for G by Boys (1894). Use of the term by T.E. Stern (1928) was misquoted as “Newton’s constant of gravitation” in Pure Science Reviewed for Profound and Unsophisticated Students (1930), in what is apparently the first use of that term. Use of “Newton’s constant” (without specifying “gravitation” or “gravity”) is more recent, as “Newton’s constant” was also used for the heat transfer coefficient in Newton’s law of cooling, but has by now become quite common, e.g. Calmet et al, Quantum Black Holes (2013), p. 93; P. de Aquino, Beyond Standard Model Phenomenology at the LHC (2013), p. 3. The name “Cavendish gravitational constant”, sometimes “Newton–Cavendish gravitational constant”, appears to have been common in the 1970s to 1980s, especially in (translations from) Soviet-era Russian literature, e.g. Sagitov (1970 [1969]), Soviet Physics: Uspekhi 30 (1987), Issues 1–6, p. 342 [etc.]. “Cavendish constant” and “Cavendish gravitational constant” are also used in Charles W. Misner, Kip S. Thorne, John Archibald Wheeler, Gravitation, (1973), 1126f. Colloquial use of “Big G”, as opposed to “little g” for gravitational acceleration dates to the 1960s (R.W. Fairbridge, The encyclopedia of atmospheric sciences and astrogeology, 1967, p. 436; note use of “Big G’s” vs. “little g’s” as early as the 1940s of the Einstein tensor G${}_{\mu \nu }$ vs. the metric tensor g${}_{\mu \nu }$, Scientific, medical, and technical books published in the United States of America: a selected list of titles in print with annotations: supplement of books published 1945–1948, Committee on American Scientific and Technical Bibliography National Research Council, 1950, p. 26). ↩

2. Cavendish determined the value of G indirectly, by reporting a value for the Earth’s mass, or the average density of Earth, as 5.448 g⋅cm${}^{-3}$. ↩

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