Quoting NASA:
--NASA - NASA Finds Earth-size Planet Candidates in the Habitable Zone
We can assume the planets in the universe will be evenly distributed as that 1/400 part Kepler analyzed. If so, then out of the 1,235 possible planets in just 1/400 of our view of the universe, 54 are in the same habitable distance from their suns as Earth. That means there could be up to 54 x 400 = 21,600 possible earth-like planets of different sizes with us in the universe.
"The findings increase the number of planet candidates identified by Kepler to-date to 1,235. Of these, 68 are approximately Earth-size; 288 are super-Earth-size; 662 are Neptune-size; 165 are the size of Jupiter and 19 are larger than Jupiter. Of the 54 new planet candidates found in the habitable zone, five are near Earth-sized. The remaining 49 habitable zone candidates range from super-Earth size -- up to twice the size of Earth -- to larger than Jupiter. The findings are based on the results of observations conducted May 12 to Sept. 17, 2009 of more than 156,000 stars in Kepler’s field of view, which covers approximately 1/400 of the sky."
--NASA - NASA Finds Earth-size Planet Candidates in the Habitable Zone
We can assume the planets in the universe will be evenly distributed as that 1/400 part Kepler analyzed. If so, then out of the 1,235 possible planets in just 1/400 of our view of the universe, 54 are in the same habitable distance from their suns as Earth. That means there could be up to 54 x 400 = 21,600 possible earth-like planets of different sizes with us in the universe.