Let us consider mass of the earth as M, radius of earth as R, and the body is at an altitude h from the surface of the earth at distance r, gh is gravity at height h from the earth’s surface. The acceleration gained by an object because of gravitational force is called its acceleration due to gravity.
Acceleration due to gravity on the surface of the earth= g = 
Gravity at height h from the earth’s surface = gh=
Distance from surface of earth (r) = Radius of earth + height from the surface of he earth
r = R + h
Therefore,
By dividing (1) / (2),the formula for acceleration due to gravity at height h from the earth’s surface is given as,
G = Universal Gravitational Constant R = radius of the earth
M = mass of the earth