An analysis of small, dim "red dwarf" stars - which make up a majority of stars in our galaxy - shows that 6% of them host such a planet. The results will appear in Astrophysical Journal. Study co-author David Charbonneau of Harvard University said the findings had implications for the search for life elsewhere.
"We now know the rate of occurrence of habitable planets around the most common stars in our galaxy," said Prof Charbonneau.
"That rate implies that it will be significantly easier to search for life beyond the solar system than we previously thought."
The hunt for exoplanets has reached a pace that is difficult to keep up with.
The Kepler space telescope has been the source of most of the known candidate exoplanets. It stares at a fixed patch of sky, watching a field of more than 150,000 stars for the tiny dips in starlight that occur if an orbiting planet passes between a star and the telescope.