September 12, 2014
Google has recently added a new feature to Hangouts on Google Plus. With this new update, the Hangout app on iOS, Android, and the web will enable you to make voice calls to anyone around the world. However, only calls made in US and Canada are free, other international calls have various rates which you can check here (there is not much difference in rates between Hangouts international calling rates and Skype, and personally I prefer Skype for making overseas calls).
"To get started on Android, just grab the new version of Hangouts (v2.3, rolling out over the next few days), then install the accompanying dialer to turn on voice calls. On iOS and the web, voice calls will be available the next time you open the app."