The global Muslim population stands at 1.57 billion, meaning that nearly 1 in 4 people in the world practice Islam, according to a report Wednesday billed as the most comprehensive of its kind.

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-Shi’a breakdown, but difficulties arose because so few countries track sectarian affiliation, said Brian Grim, the project’s senior researcher.

As a result, the Shi’a numbers are not as precise; the report estimates that Shi’a represent between 10 and 13 percent of the Muslim population, in line with or slightly lower than other studies. As much as 80 percent of the world’s Shi’a population lives in four countries: Iran, Pakistan, India and Iraq.

The report provides further evidence that while the heart of Islam might beat in the Middle East, its greatest numbers lie in Asia: More than 60 percent of the world’s Muslims live in Asia.

About 20 percent live in the Middle East and North Africa, 15 percent live in Sub-Saharan Africa, 2.4 percent are in Europe and 0.3 percent are in the Americas. While the Middle East and North Africa have fewer Muslims overall than Asia, the region easily claims the most Muslim-majority countries.

While those population trends are well established, the large numbers of Muslims who live as minorities in countries aren’t as scrutinized. The report identified about 317 million Muslims — or one-fifth of the world’s Muslim population — living in countries where Islam is not the majority religion.

About three-quarters of Muslims living as minorities are concentrated in five countries: India (161 million), Ethiopia (28 million), China (22 million), Russia (16 million) and Tanzania (13 million).

In several of these countries — from India to Nigeria and China to France — divisions featuring a volatile mix of religion, class and politics have contributed to tension and bloodshed among groups.

The immense size of majority-Hindu India is underscored by the fact that it boasts the third-largest Muslim population of any nation — yet Muslims account for just 13 percent of India’s population.

“Most people think of the Muslim world being Muslims living mostly in Muslim-majority countries,” Grim said. “But with India … that sort of turns that on its head a bit.”