Here we offer an interactive calculator that estimates Habitable Zones around Main-sequence stars with effective temperatures in the range of 2600 K - 7200 K. The default values are for the Sun. If you don't know the stellar luminosity, just enter stellar effective temperatures and keep luminosity = 0. That will give just Habitable stellar flux boundaries. If you provide luminosities, you can also obtain habitable zone distances in AU. If you want to calculate HZs for a number of stars, download this FORTRAN code.
If you use the calculator or the code, please acknowledge the following paper:
Kopparapu et al. (2013), Habitable Zones around Main-sequence stars: New Estimates. Astrophysical Journal, 765, 131. (arXiv link)