IIRC, the method often used for estimating the number of stars in the Milky Way is the simplest: taking the mass of the Galaxy in solar masses and dividing that by some reasonable mass figure. If the Galaxy has a mass of 100 billion solar masses, then if you divide that by one solar mass, you get 100 billion stars. However, we all know that the "average star" in the Galaxy is *not* the size of the Sun, so as the figure goes down, the number of potential stars goes up. Half a solar mass, 200 billion, etc.<br /><br />As Harmonicaman said, we really don't know how many stars are in our Galaxy, only that there are probably over 100 billion of them. This is because we don't know the average mass of a galactic star, nor how much of the Galaxy's mass is actually tied up in stars versus just as gas or dark matter. Finally, including brown dwarfs in the final estimate may greatly increase the answer, even though they aren't technically stars.