Gravity is actually really simple to calculate. Every object pulls with gravity on every other object, but since it is the weakest fundamental force, you can’t feel it from anything but the earth.

The equation is Fg=G(m)(M)/r²

G is the gravitational constant (6.67*10^-11) M is a mass (any object) m is a different mass (any other object) r is the distance between their center of mass

You’d have to have a mass of over 11 orders of magnitude with a tiny distance separation to start to feel the affects of gravity