Acceleration due to gravity (g)
g is the acceleration due to gravity: how quickly a falling object near Earth’s surface speeds up, about 9.80 metres per second squared (32.2 ft/s²). The fixed standard value, written gₙ, is exactly 9.806 65 m/s².
Easily confused with
How to read it
OpenStax’s University Physics gives g ≈ 9.80 m/s² for a free-falling object near Earth’s surface and calls the force behind it the object’s weight, mg. The value changes with height and place. OpenStax works out g at the height of the International Space Station as 8.67 m/s², so that astronauts there still have 88% of their weight, and shows that Earth’s rotation makes the apparent weight differ between the poles and other latitudes. For definitions a fixed number is used: the standard acceleration of gravity gₙ = 9.806 65 m/s², which NIST’s 2022 CODATA table lists as exact. It is the number behind the kilogram-force; NIST’s Guide for the Use of the SI gives 1 kgf = 9.806 65 N.
Also searched as: 9.8 m/s2, acceleration due to gravity symbol, acceleration of free fall, g, g in physics, gn, little g, standard gravity.
g, g and G
The italic g is the acceleration. The upright g is the gram, a unit symbol, and NIST’s guide prints unit symbols upright. Capital G is the gravitational constant, which sets the strength of gravity everywhere rather than the pull at Earth’s surface.
Read next
- Next in Physics and chemistry symbolsElementary charge (e)e is the elementary charge: the charge of one proton, and the size of the charge of one electron. It is exactly 1.602 176 634 × 10⁻¹⁹ coulombs.
- The same shape in Notable US coinsKennedy half dollarThe US half dollar with John F. Kennedy’s portrait, first issued in 1964 after his assassination. 1964 halves are 90% silver, 1965 to 1970 are 40% silver, and from 1971 there is no silver.
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The same shape elsewhere
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Sources
- University Physics Volume 1, 13.2 Gravitation Near Earth’s Surface, OpenStax (Rice University), Weight; Example 13.5; Results Away from the Equator
- CODATA Value: standard acceleration of gravity, The NIST Reference on Constants, Units and Uncertainty (2022 CODATA), National Institute of Standards and Technology, standard acceleration of gravity
- Guide for the Use of the International System of Units (SI), NIST Special Publication 811 (2008), National Institute of Standards and Technology, Table 10; Sec. 10.2.2; Sec. B.8
Researched, edited and approved by Rory Hansen before publishing. Last reviewed October 9, 2026. How we research
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