CIA gives 18.8%, so about 1.5 billion. [1]

But this number is dubious as it's largely from self response. Here [2] is a list by country. So 25% of Thais, 50% of Ukrainians, 50% of Poles, and so on "speak English."

In the sense of being able to say hello, thank you, and introduce themselves that is probably true. But "my name is Bob" maketh not a common tongue. If we narrowed it down to the percent of people that could hold a basic conversation, the number would plummet precipitously, likely leaving Mandarin at the top.

[1] - https://en.wikipedia.org/w/index.php?title=List_of_languages...

[2] - https://en.wikipedia.org/wiki/List_of_countries_by_English-s...