Isolating how many people speak a language can be difficult, especially when it comes to English. Counting native speakers is easier, but it becomes more difficult to count those who speak it as a foreign language: Does the waiter in the Chinese restaurant or the taxi driver who speaks 300 words of English count as a "speaker"?
The British Council, based on estimates by global English expert David Crystal, offers the following extremely rough--and often overlapping--breakdown of English speakers in the world:
Speakers of English as a first (and often only) language: about 375 million.
Speakers of English as a second language, which may not be their indigenous language but is used within their own country to communicate with others: about 375 million.
Speakers of English as a foreign language who have studied it to communicate with people outside their own cultures: about 750 million.
Total estimated speakers of English worldwide: roughly 1.5 billion.
Source: "The Future of English?" published by the British Council.