Although it is impossible to be absolutely sure, there are several indicators for estimating the approximate size of the Internet and World Wide Web. The most common is number of users.
There are quite a few companies who attempt to measure the Internet's usage: the Internet Society is one of them.
All of them use custom techniques of polling, web server, and other measures
This is a compilation of from Internet Live Stats:
Total Internet Human Usage, November 2015
1. 3.1 billion: the total estimated number of unique individuals who are actively using the Internet.
2. 279.1 million: the estimated number of USA residents on Internet.
3. 646.6 million: the estimated number of China residents on the Internet.
4. 86.4 million: the estimated number of Russian residents on the Internet.
5. 108.1 million: the estimated number of Brazil residents on Internet.
Historical Comparison: Internet Usage in One Month, by Country, Oct 2005:
1. Australia: 9.8 million
2. Brazil: 14.4 million
3. Switzerland 3.9 million
4. Germany 29.8 million
5. Spain 10.1 million
6. France 19.6 million
7. Hong Kong 3.2 million
8. Italy 18.8 million
9. Netherlands 8.3 million
10. Sweden 5.0 million
11. United Kingdom 22.7 million
12. United States 180.5 million
13. Japan 32.3 million
According to these statistics, it is safe to conclude that the Internet is a daily tool for millions of people worldwide. When it first started in 1989, Internet had 50 people sharing web pages.
Today, over 3 billion people use the Web every week as a part of their lives.
Víctor Hernández González