Set to:

Interactive Drake Equation

Average number of new stars formed in the Milky Way annually (about 6 according to NASA):

Proportion of stars which have one or more planets (at least 10%, probably more):

Average number of planets/moons per solar system where basic life could potentially appear:

Percentage of life-compatible planets where life eventually does appear:

Percentage of planets where intelligent life evolves:

Percentage of civilizations which eventually send signals into space (TV, radio, etc.):

Average number of years that an advanced civilization will send such signals:

Probable communicating civilizations in our galaxy:

N= R*x f_px n_ex f_lx f_ix f_cx L

From Wikipedia:

N is the number of civilizations in our galaxy with which we might hope to be able to communicate.
R* is the average rate of star formation in our galaxy.
f_p is the fraction of those stars that have planets.
n_e is the average number of planets that can potentially support life per star that has planets.
f_l is the fraction of the above that actually go on to develop life at some point.
f_i is the fraction of the above that actually go on to develop intelligent life.
f_c is the fraction of civilizations that develop a technology that releases detectable signs of their existence into space.
L is the length of time such civilizations release detectable signals into space.