This is a hard question and depends on what you consider to be Earth-like. Planets that have a similar mass and composition to Earth are likely relatively common in other solar systems, but the ones we have found so far are typically too close to their stars to host liquid water oceans. We also don't know how many of those planets could have magnetic fields to protect their surfaces from damaging particles, or moons to stabilize their rotation. In short, there are lots of things that make Earth such a special planet, and we do not know enough about planets around other stars to confidently say how many planets like ours there are out there in the galaxy.