# What Is a Gravitational Constant in English Units?

**A gravitational constant has a value of 6.673 84 x 10^-11 m^3 kg^-1 s^-2 in English units, which can also be written as G = 6.673 x 10^-11 N m^2 kg^-2.** This is also called the Newtonian constant of gravitation.

The gravitational constant has a relative standard uncertainty of 0.000 80 x 10^-11 m^3 kg^-1 s^-2 and a concise form of 6.673 84(80) x 10^-11 m^3 kg^-1 s^-2.

The gravitational constant is most commonly used in equations such as F = (G x m1 xm2) / r2 where the F = force of gravity, the G = gravitational constant, the m1 = mass of the first object, m2 = mass of the second object and r = the separation between the two masses.

The gravitational constant is primarily used in the field of physics and was determined through empirical value. Experiments, studies and observations allowed scientists to arrive at this number. However, the gravitational constant was originally introduced as a concept by Isaac Newton. He published in the Philosophiae Naturalis Principia Mathematica in 1687 with the theory, but he did not actually observe it in an experiment until 1798. Henry Cavendish was the first to successfully measure the gravitational constant and assign a value to it.