An estimate for the number of planets with intelligent communicative extraterrestrial life can be based on the Drake equation.   It expresses the probability of intelligent life as the product of factors such as the fraction planets that might be habitable and the fraction of planets on which life might arise....

Fomula:

N = R*  x  fp  x  ne  x  fl  x  fi  x  fc  x  L

with

N =  the number of civilizations in our galaxy with which communication might be possible (i.e. which are on our current past light cone);
R* = the rate of formation of suitable stars (stars like our Sun)
fp = the fraction of those stars that have planets
ne = the average number of planets that can potentially support life per star that has planets
fl = the fraction of planets that could support life that actually develop life at some point
fi = the fraction of planets with life that actually go on to develop intelligent life (civilizations)
fc = the fraction of civilizations that develop a technology that releases detectable signs of their existence into space
L = the length of time for which such civilizations release detectable signals into space


Current estimates suggest that solution of the equation is  15,600,000 civilizations in our Milky Way galaxy....

Details can be found on the internet:   https://en.wikipedia.org/wiki/Drake_equation