What is Newton's constant G?
G is the gravitational constant.
The universal law of gravitation says that the force of attraction between 2 bodies is proportional to the product of their masses,
So to get the the force of attraction
G has both a number as part of it and a combination of units. The constant G to make the formula come out in Newtons is:
The units that are part of that constant are necessary to allow the units from the 2 masses and the square of the radius to be cancelled leaving Newtons as the only units on the result.
It is similar to the weight of a mass here on Earth. The weight is proportional to the mass. But, to get the weight in Newtons, you have to multiply by a constant of proportionality, which in that case is the acceleration due to gravity at the Earth's surface
The acceleration due to gravity at the Earth's surface is given by:
I hope this helps,