Almost 25 percent of Internet users have made phone calls via Internet Protocol services such as Skype and Vonage, according to a study (PDF) released yesterday by Pew Internet.

Of the U.S. adult population in general, 19 percent had made Internet calls, based on the poll. On an average day, around 5 percent of Internet users are likely to make a phone call online, the poll found.

The latest findings show a dramatic increase over previous Pew surveys that asked similarly-phrased questions about online phone calls.

In February of 2007, Pew found that only 8 percent of Internet users had made phone calls via the Internet and that around 2 percent made them on any given day. Throughout the 2000s, Pew conducted similar polls and each time found that at most only around 10 percent said they had make phone calls online, while less than 1 percent had done so on any given day.

Online video calls have also increased over time. In this latest survey, around 7 percent of mobile phone users said they had used their devices for video calls or online chats.

Drilling down to some of the specific results, urban and suburban Internet users were more likely than their rural counterparts to make online phone calls, while younger users were also a bit ahead of older users in hopping onto the Internet to make a call.

To compile its study, Pew included results from 846 users from a national survey on landline and cell phone use that targeted 2,277 adults in the U.S. between April 26 and May 22.