Gravitational Field Strength

Gravitational field strength at a point is defined as the gravitational force per unit mass:

$g = \frac{F}{m}$

On the Earth’s surface, $g \approx 9.8$ N/kg. On the Moon, $g \approx 1.6$ N/kg.

$g$ is also numerically equal to the acceleration due to gravity (9.8 m/s$^2$ on Earth). The two quantities have the same numerical value but different units depending on context.

$g$ decreases with altitude above the surface and varies slightly across the Earth’s surface.