According to Pew Research Center estimates for 2020, which religion had the largest number of adherents worldwide?
Choose an answer, then check it.
History · Foundations
Major World Religions
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In 30 seconds
Historians study religions descriptively: they record when and where a tradition formed, what it teaches, its sacred texts, and how many people follow it, without judging whether any of its claims are true. By adherents, the five largest traditions are Christianity, Islam, Hinduism, Buddhism, and Judaism. Others, including Sikhism, Jainism, Chinese and Indigenous traditions, and the growing religiously unaffiliated People who report no particular religion, including atheists and agnostics; a demographic category rather than a single religion. Full entry →, round out a diverse global picture that survey data help us measure.
Why this matters
Nearly every field a college student enters, from history and literature to medicine, law, and international relations, involves people whose lives are shaped by religion. Being able to describe the major traditions accurately and even-handedly, without endorsing or dismissing any of them, is a basic literacy for reading the past and working across cultures. This overview also teaches a transferable habit of mind: separating what can be documented, such as when a tradition formed and how many follow it, from questions of belief that evidence cannot settle. That discipline protects you from both stereotype and false certainty.
The college version
Studying religion as a historian
A historian approaches religion the way any other human phenomenon is approached: as something people do, build, write down, and pass on. The historian's questions are descriptive and evidentiary. Where and when did a tradition take shape? Who, if anyone, is regarded as its founder, and in what period? What does it teach, and which texts does it hold sacred? How many people follow it today, and where do they live? Crucially, the historian does not ask whether a religion's claims about God, the cosmos, or salvation are true. Those are questions of faith and philosophy that documentary evidence cannot settle, and treating them as history would mean privileging one tradition over another. So a careful writer states what a tradition holds ('Muslims regard the Qur'an as the word of God revealed to Muhammad') rather than asserting the claim as fact. This even-handed stance is not indifference; it is precision. It lets us compare traditions fairly and describe each with the same seriousness and respect.
The five largest traditions
By number of adherents, five traditions dominate the global picture. Hinduism has no single founder; it grew out of the Vedic religious traditions of the Indian subcontinent over the second and first millennia BCE, and its foundational texts include the Vedas and Upanishads. Its ideas commonly include dharma (moral and cosmic order), karma (action and consequence), and rebirth. Buddhism traces to Siddhartha Gautama, called the Buddha, traditionally placed in the sixth to fifth century BCE in South Asia, though some modern scholars date his life somewhat later; its teachings center on the causes of suffering and a path beyond it, and its scriptures include the Tripitaka (Pali Canon). Judaism formed among the ancient Israelites in the southern Levant during the first and second millennia BCE; it centers on a covenant with one God, and its scripture is the Hebrew Bible (Tanakh), whose first section is the Torah. Christianity began in the first century CE in Roman Judea, rooted in the life and teachings of Jesus of Nazareth, whom Christians hold to be the Son of God; its scripture is the Bible, comprising the Old and New Testaments. Islam arose in the seventh century CE on the Arabian Peninsula, associated with the Prophet Muhammad; its scripture is the Qur'an, and the Hijra, the migration from Mecca to Medina in 622 CE, is a foundational event. Christianity, Islam, and Judaism are often grouped as the Abrahamic traditions because each looks back to the figure of Abraham.
Beyond the five: other traditions and the unaffiliated
The largest five do not exhaust the map. Sikhism originated in the Punjab region of South Asia in the late fifteenth to early sixteenth century CE, associated with Guru Nanak (1469-1539), and its scripture is the Guru Granth Sahib. Jainism is an ancient tradition of the Indian subcontinent emphasizing non-violence (ahimsa), associated in its classical form with Mahavira. In China, Daoist and Confucian traditions, together with widespread folk practice, have shaped religious life for more than two millennia. Across every continent, Indigenous and folk religions remain tied to particular peoples and places. Finally, a large and growing share of people are religiously unaffiliated, sometimes called 'nones.' This is not itself a religion but a category that includes atheists, agnostics, and people with no particular affiliation; some still hold spiritual beliefs. Pew Research Center estimated that in 2020 the unaffiliated made up about 24.2 percent of the world's population, the third-largest group after Christians and Muslims.
Universalizing versus ethnic religions
Scholars of religion and geography often sort traditions into two broad kinds. A universalizing religion A religion that presents its message as intended for all people and actively welcomes converts from any background. Full entry → presents its message as meant for everyone and actively invites members from any background, often through missionary activity, trade, and conversion; Christianity, Islam, and Buddhism are the classic examples, and their followers are spread widely across the globe. An ethnic religion A religion tied to a specific people, culture, or place, typically joined by birth and community rather than by conversion. Full entry → is bound up with a particular people, culture, or homeland and generally does not seek converts; membership usually comes through birth and community rather than recruitment. Judaism, Hinduism, and many folk and Indigenous religions fit this pattern, and their adherents tend to be concentrated in specific regions. The distinction is a useful generalization, not an iron law: traditions can carry features of both, and individual communities vary. Used carefully, though, it explains a great deal about why some traditions are dispersed worldwide while others remain rooted in one place.
Reading the numbers with care
adherent A person counted as belonging to or following a particular religion in a survey or estimate. Full entry → figures are estimates, not a census of belief, so they should always be dated and attributed. According to Pew Research Center estimates for 2020, published in June 2025, Christians numbered about 2.3 billion (28.8 percent of the world population), Muslims about 2.0 billion (25.6 percent), the religiously unaffiliated about 1.9 billion (24.2 percent), Hindus about 1.2 billion (14.9 percent), Buddhists about 324 million (4.1 percent), adherents of other religions about 174 million (2.2 percent), and Jews about 14.8 million (0.2 percent). The same study found that between 2010 and 2020 Muslims were the fastest-growing major group, increasing by about 347 million, while Buddhists were the only major group with fewer people at the end of the decade than at the start. Numbers like these come from combining censuses, surveys, and population registers, and different organizations define categories differently, so counts vary between sources. Citing the survey and the year is what keeps a factual statement honest.
Eli explains
The same idea, in plain words
Explain it like I’m 10
Imagine you are making a fair guidebook to the world's religions. Your job is not to say which one is right. Your job is to write down, for each tradition, where and when it started, what its followers believe, which book they treasure, and how many people follow it. Some religions, like Christianity, Islam, and Buddhism, invite anyone to join. Others, like Judaism and Hinduism, are woven into a particular people and place, so you usually grow up in them. And a big group of people today follow no religion at all.
Picture it like this
Think of the world's religions like the world's languages. A good language atlas tells you where each language is spoken, how it is written, and how many speakers it has, without declaring any language the 'best' one. A fair guide to religions does the same: it maps and describes, but it does not rank.
Where the picture stops working
The analogy has limits. Languages are mainly tools for communication, while religions make claims about meaning, right and wrong, and what happens after death, so people often hold them far more deeply than they hold a language. And unlike languages, some religions actively seek new followers while others do not, so the map of 'who joins how' works differently.
Worked example
Suppose a historian is handed a claim to evaluate: 'Islam is the world's oldest religion and its holiest.' Working descriptively, the historian separates the parts. 'Oldest' is a datable question: Islam arose in the seventh century CE, while Judaism and Hinduism took shape more than a thousand years earlier, so the age claim is simply false. 'Holiest' is a truth-and-value claim that no document can settle and that a historian will not rank, so it is set aside as outside the discipline. The historian then rewrites the sentence into something evidence supports: 'Islam, which began in the seventh century CE in Arabia, is today one of the two largest religions, with about 2.0 billion adherents in 2020 according to Pew Research Center.' Notice what changed: a dated origin replaced a false superlative, a value judgment was removed, and the population figure was attributed and dated.
Key takeaway
Historians describe religions rather than judge them: for each tradition they record its origins, core ideas, sacred texts, and dated, attributed adherent numbers, and they distinguish universalizing religions that seek converts from ethnic religions bound to a particular people or place.
Quick check
3 questions here, of 5 in this lesson’s practice set. Answers stay hidden until you check.
In Pew Research Center's 2020 estimates, the religiously unaffiliated made up about 24.2 percent of the world's population. Where did that place them among global groups?
Choose an answer, then check it.
Which statement best captures the distinction between a universalizing religion and an ethnic religion?
Choose an answer, then check it.
Study tools & related lessonsYou’ll learn to · Common mistakes · Easily confused · Key vocabulary · Related
You’ll learn to
- Explain how a historian describes a religion without making or evaluating a truth claim.
- Identify the origins, core ideas, and principal sacred texts of Christianity, Islam, Hinduism, Buddhism, and Judaism.
- Distinguish universalizing religions from ethnic religions and give examples of each.
- Interpret dated, attributed adherent figures and explain why such counts are estimates.
- Name major traditions beyond the largest five, including the religiously unaffiliated.
Common mistakes
Treating a religion's teaching as a historical fact, for example writing 'God revealed the Qur'an to Muhammad' as a plain statement.
Attribute the belief to its holders: 'Muslims believe the Qur'an was revealed to Muhammad.' Historians describe what traditions claim without asserting the claim.
Assuming the largest religion is also the oldest, or ranking traditions by importance.
Age, size, and significance are separate. Judaism and Hinduism are far older than the larger Christianity and Islam, and historians rank traditions only by measurable things like adherent counts, which must be attributed.
Giving an adherent figure with no date or source, such as 'there are 2 billion Muslims.'
Cite the survey and year, for example 'about 2.0 billion Muslims in 2020 (Pew Research Center),' because counts are estimates that change and differ by source.
Calling every large tradition a religion that seeks converts.
Distinguish universalizing religions, which invite converts, from ethnic religions like Judaism and Hinduism, which are generally joined by birth and community rather than recruitment.
Listing the 'religiously unaffiliated' as if it were a single religion.
The unaffiliated are a demographic category that includes atheists, agnostics, and people with no particular affiliation, not one organized tradition.
Easily confused
Universalizing religion vs. Ethnic religion
A universalizing religion (Christianity, Islam, Buddhism) presents its message for everyone and seeks converts; an ethnic religion (Judaism, Hinduism, many folk traditions) is tied to a particular people or place and is usually joined by birth.
Established historical fact vs. Religious truth claim
When and where a tradition formed can be documented and is the historian's domain; whether its teachings are true is a matter of faith that historians describe but do not adjudicate.
Judaism vs. Christianity
Both are Abrahamic and monotheistic, but Judaism formed among the ancient Israelites more than two millennia earlier and centers on the Tanakh, while Christianity began in first-century Roman Judea around the life of Jesus and adds the New Testament.
Key vocabulary
- adherent
- A person counted as belonging to or following a particular religion in a survey or estimate.
- universalizing religion
- A religion that presents its message as intended for all people and actively welcomes converts from any background.
- ethnic religion
- A religion tied to a specific people, culture, or place, typically joined by birth and community rather than by conversion.
- Abrahamic religions
- Judaism, Christianity, and Islam, grouped together because each traces its heritage to the figure of Abraham and worships one God.
- monotheism
- The belief in a single God, as in Judaism, Christianity, and Islam.
- sacred text
- A writing a tradition regards as authoritative or holy, such as the Vedas, the Tanakh, the Bible, or the Qur'an.
- religiously unaffiliated
- People who report no particular religion, including atheists and agnostics; a demographic category rather than a single religion.
- religious demography
- The study of the size, distribution, and change over time of religious populations.
Sources & references
- How the Global Religious Landscape Changed From 2010 to 2020 — Pew Research Center
- World History, Volume 1, to 1500 (Chapter 5 and related section summaries on early religions) — OpenStax (Rice University)
- People, Places, and Cultures, 3.4 Geography of World Religions — Oklahoma State University Libraries (R. Adam Dastrup; Raymon Huston, ed.)
- Encyclopaedia Britannica entries on Islam, Muhammad, Sikhism, Buddhism, and Judaism (founding facts) — Encyclopaedia Britannica
EliExplains lessons are original prose written from the open, credible references above. See Copyright & Licensing.
Researched 2026-08-19
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