* Different definitions of "speak English": Do we mean native speakers, fluent speakers, or those who can understand basic English?
* Lack of precise data: Gathering reliable information about language proficiency worldwide is a complex task.
* Constantly changing numbers: The number of English speakers is constantly changing due to globalization, education, and other factors.
However, estimates from reputable sources suggest that roughly 1.5 billion people speak English as a first language and around 1 billion speak it as a second language. This puts the total number of English speakers somewhere between 2.5 and 3.5 billion**.
It's important to remember that these are estimations, and the actual number could be higher or lower.