One of the simplest and most popular ways to make calls from a PC for free is Google Voice. This service is free for Google users and can be used to make domestic calls within the United States and Canada for free as well as international calls at low rates. Navigate to google.com/voice. If prompted, sign up for a phone number, then click the call button on the top left to make a call.
Creating a Google Voice account lets you make phone calls from other Google services as well. For example, you can add a phone number to a Google Voice hangout session by clicking to invite a participant and choosing the Add Telephone option. Similarly, Google Voice phone numbers can be used to make calls from Gmail. If an email contains a phone number, click the phone number. After the dial pad appears, click Call. Alternatively, click the Call Phone icon in Google Chat on the bottom left of the Gmail window. Enter a phone number into the box that appears and press Call.
Some other services that allow users to make phone calls from their PCs are Rebtel, Skype and Nimbuzz; however, when using Skype and Nimbuzz, both users must have the app in order for calls to be free.
PC to phone programs are required to call traditional phones, and app to phone programs can facilitate free calls from a mobile device to a standard phone. PC to PC programs allow users to make free calls between computers, and app to app programs connect people who use the same particular software.