Religious Affiliation
Roughly 31% of the world identifies as Christian, 25% as Muslim, 15% as Hindu, 7% as Buddhist, with 16% religiously unaffiliated. Christianity is the largest religion overall; Islam the fastest-growing due to demographics; the unaffiliated growing in Western countries and parts of Asia. Pew Research projects Muslims to roughly equal Christians by 2070.
Key insights
Christianity is the largest and most geographically spread
Christianity has the most geographically diverse footprint of any major religion — significant communities on every inhabited continent. Sub-Saharan Africa is now the largest single Christian region and the fastest-growing (~700M Christians, double the US). The center of gravity has shifted south of the equator. Catholicism remains the largest single tradition globally; Pentecostal/charismatic Christianity is the fastest-growing variant.
Islam is growing fastest demographically
Higher fertility rates among Muslim-majority populations drive faster Islamic growth than other major religions. Pew projects Muslims to grow from ~25% (2020) to ~30% (2050). Roughly 60% of the world's Muslims live in Asia-Pacific (Indonesia, Pakistan, Bangladesh, India). Sub-Saharan Africa has the fastest-growing Muslim population. The 'Middle East' image of Islam masks where most Muslims actually live.
The religiously unaffiliated are the third-largest group
Religiously unaffiliated ('nones' — atheists, agnostics, those identifying with no religion) number ~1.2 billion. Concentrated in: East Asia (China is ~50% unaffiliated), Western Europe, North America. The unaffiliated are growing in advanced economies and parts of Asia, shrinking demographically in the global south. By 2050 Pew projects unaffiliated share to fall slightly globally despite growing in absolute terms.
Major religions — share of world population (2024)
% of global population
Key Finding: Christianity, Islam and the unaffiliated together account for ~72% of humanity.
Projected world religious affiliation 2020 vs 2050
% of world population, Pew projections
Key Finding: Islam projected to grow faster than other major religions; Christianity roughly stable; unaffiliated share declining slightly due to lower fertility.
Methodology & caveats
How religious affiliation is measured
Self-identification on national censuses (where allowed) and standardized surveys (Pew Religious Landscape, World Values Survey). 'Religious' status is independent of practice — a person can identify as Christian without attending church. Practice rates are typically much lower than affiliation rates in advanced economies.
Why China is hard to measure
Chinese government religious-affiliation data is unreliable. Estimates of Chinese Christians range from 30M (official) to 100M+ (Western estimates). Underground house-church communities are not registered. Folk-religion practices overlap with Buddhism and Daoism. Pew uses ~5% Christian, ~2% Muslim, ~18% Buddhist, ~50% unaffiliated for China — but these carry wide uncertainty.
Sub-group dynamics
Within Christianity: Catholic (~50%), Protestant (~37%), Orthodox (~12%), other. Within Islam: Sunni (~85-90%), Shia (~10-15%). Within both, sub-traditions vary enormously in theology, practice, geographical concentration. Headline religious-affiliation statistics aggregate enormous internal diversity that matters for political and social outcomes.