The Pew Forum on Religion and Public Life report provides a precise number for a population whose size has long has been subject to guesswork, with estimates ranging anywhere from 1 billion to 1.8 billion.
The project, three years in the making, also presents a portrait of the Muslim world that might surprise some.
For instance, Germany has more Muslims than Lebanon, China has more Muslims than Syria, Russia has more Muslims than Jordan and Libya combined, and Ethiopia has nearly as many Muslims as Afghanistan.
"This whole idea that Muslims are Arabs and Arabs are Muslims is really just obliterated by this report," said Amaney Jamal, an assistant professor of politics at Princeton University who reviewed an advance copy.
Pew officials call the report the most thorough on the size and distribution of adherents of the world's second largest religion behind Christianity, which has an estimated 2.1 billion to 2.2 billion followers.
The arduous task of determining the Muslim populations in 232 countries and territories involved analyzing census reports, demographic studies and general population surveys, the report says. In cases where the data was a few years old, researchers projected 2009 numbers.
The report also sought to pinpoint the world's Sunni-Shiite breakdown, but difficulties arose because so few countries track sectarian affiliation, said Brian Grim, the project's senior researcher.