As of 2010, Christianity was the religion with the most followers worldwide, followed by Islam (Muslims) and Hinduism. In the forty years between 2010 and 2050, it is projected that the landscape of world religions will undergo some noticeable changes, with the number of Muslims almost catching up to Christians. The changes in population sizes of each religious group is largely dependent on demographic development, for example, the rise in the world's Christian population will largely be driven by population growth in Sub-Saharan Africa, while Muslim populations will rise across various regions of Africa and South Asia. As India's population is set to grow while China's goes into decline, this will be reflected in the fact that Hindus will outnumber the unaffiliated by 2050. In fact, India may be home to both the largest Hindu and Muslim populations in the world by the middle of this century.

In 2020, around 28.8 percent of the global population were identified as Christian. Around 25.6 percent of the global population identify as Muslims, followed by 14.9 percent of global populations as Hindu. The number of Muslims increased by 347 million, when compared to 2010 data, more than all other religions combined.

Christianity is the major religion in numerous African countries. As of 2024, around 96 percent of the population of Zambia was Christian, representing the highest percentage on the continent. Seychelles and Rwanda followed with roughly 95 percent and 94 percent of the population being Christian, respectively. While these countries present the highest percentages, Christianity was also prevalent in many other African nations. For instance, in South Africa, Christianity was the religion of nearly 85 percent of the people, while the share corresponded to 71 percent in Ghana. Religious variations across Africa Christianity and Islam are the most practiced religions in Africa. Christian adherents are prevalent below the Sahara, while North Africa is predominantly Muslim. In 2020, Christians accounted for around 60 percent of the Sub-Saharan African population, followed by Muslims with a share of roughly 30 percent. In absolute terms, there were approximately 650 million Christians in the region, a number forecast to increase to over one billion by 2050. In contrast, Islam is most prevalent in North Africa, being the religion of over 90 percent of the population in Algeria, Morocco, Tunisia, and Libya. Christianity in the world As opposed to other religions, Christianity is widely spread across continents worldwide. In fact, Sub-Saharan Africa, Latin America and the Caribbean, and Europe each account for around 25 percent of the global Christian population. By comparison, Asia-Pacific and North America make up 13 percent and 12 percent of Christians worldwide, respectively. In several regions, Christians also suffer persecution on religious grounds. Somalia and Libya presented the most critical situation in Africa in 2021, reporting the strongest suppression of Christians worldwide just after North Korea and Afghanistan.

The World Religion Project (WRP) aims to provide detailed information about religious adherence worldwide since 1945. It contains data about the number of adherents by religion in each of the states in the international system. These numbers are given for every half-decade period (1945, 1950, etc., through 2010). Percentages of the states' populations that practice a given religion are also provided. (Note: These percentages are expressed as decimals, ranging from 0 to 1, where 0 indicates that 0 percent of the population practices a given religion and 1 indicates that 100 percent of the population practices that religion.) Some of the religions are divided into religious families. To the extent data are available, the breakdown of adherents within a given religion into religious families is also provided.

The project was developed in three stages. The first stage consisted of the formation of a religion tree. A religion tree is a systematic classification of major religions and of religious families within those major religions. To develop the religion tree we prepared a comprehensive literature review, the aim of which was (i) to define a religion, (ii) to find tangible indicators of a given religion of religious families within a major religion, and (iii) to identify existing efforts at classifying world religions. (Please see the original survey instrument to view the structure of the religion tree.) The second stage consisted of the identification of major data sources of religious adherence and the collection of data from these sources according to the religion tree classification. This created a dataset that included multiple records for some states for a given point in time. It also contained multiple missing data for specific states, specific time periods and specific religions. The third stage consisted of cleaning the data, reconciling discrepancies of information from different sources and imputing data for the missing cases.

The National Religion Dataset: The observation in this dataset is a state-five-year unit. This dataset provides information regarding the number of adherents by religions, as well as the percentage of the state's population practicing a given religion.

From 2022 to 2060, the worldwide population of Muslims is expected to increase by 45.7 percent. For the same period, the global population of Buddhists is expected to decrease by 12.2 percent.

The Bahá’í faith is one of the world's youngest major religions, having been founded in 19th century Persia (now Iran) by the prophet Bahá’u’lláh. Bahá’u’lláh had been a follower of a merchant called the Báb, who had developed a substantial following in Persia after claiming to be a manifestation of god. This small but growing religion was brutally suppressed by the Shia Muslim authorities in Persia, with the Báb himself being executed in 1850. Following this, Bahá’u’lláh fled into exile in Baghdad, in present-day Iraq, where he began to preach that he was the next in the line of God's messengers after the Báb. Both of the prophets claimed the lineage of all Abrahamic religions, combining beliefs from Islam, Christianity, and Judaism. Bahá’u’lláh was eventually forced to settle in the coastal city of ‘Akká, Palestine (now Acre, Israel) where he died in 1892. The site of his death became the central place of pilgrimage in the Bahá’í faith, and is why the center of the religion is today in the nearby city of Haifa. Beliefs of the Bahá’í The Bahá’í are perhaps unique for a major religion, as rather than emphasizing the correctness of their own beliefs over other religions, followers of Bahá’í believe that there is truth in all world religions and that there should be peace and harmony among the different faiths. Bahá’ís recognize the prophets and messengers of the different world religions as all part of the same process of revelation by God to humanity. While they believe in plurality among those who bring God's message, the Bahá’í are monotheistic and believe in only one god, rather than multiple. Bahá’u’lláh taught that the different religions developed to convey the same message of God, but in different societies and time periods, meaning that the message has been delivered in different ways to suit the needs of the time and place. The key teachings of the Bahá’í faith include the unity of science and religion, equality between different peoples and religions, the importance of education and tolerance, and the unity of world religions due to the oneness of God. Today it is estimated that over five million people follow the teachings of the Báb and Bahá’u’lláh worldwide.

As of 2020, Christianity was the largest religion in the world, with around 2.5 billion believers. In the second place was Islam, with around 1.9 billion adherents.

Islam is the major religion in many African countries, especially in the north of the continent. In Comoros, Libya, Western Sahara, at least 99 percent of the population was Muslim as of 202. These were the highest percentages on the continent. However, also in many other African nations, the majority of the population was Muslim. In Egypt, for instance, Islam was the religion of 79 percent of the people. Islam and other religions in Africa Africa accounts for an important share of the world’s Muslim population. As of 2019, 16 percent of the Muslims worldwide lived in Sub-Saharan Africa, while 20 percent of them lived in the Middle East and North Africa (MENA) region. Together with Christianity, Islam is the most common religious affiliation in Africa, followed by several traditional African religions. Although to a smaller extent, numerous other religions are practiced on the continent: these include Judaism, the Baha’i Faith, Hinduism, and Buddhism. Number of Muslims worldwide Islam is one of the most widespread religions in the world. There are approximately 1.9 billion Muslims globally, with the largest Muslim communities living in the Asia-Pacific region. Specifically, Indonesia hosts the highest number of Muslims worldwide, amounting to over 200 million, followed by India, Pakistan, and Bangladesh. Islam is also present in Europe and America. The largest Islamic communities in Europe are in France (5.72 million), Germany (4.95 million), and the United Kingdom (4.13 million). In the United States, there is an estimated number of around 3.45 million Muslims.

Sikhism is a religion that originated on the Indian subcontinent during the fifteenth century. Sikhs follow the teachings of 'gurus', who descend from the first guru Guru Naruk who established the faith. Followers of Sikhism are monotheists, believing in only one god, and other core beliefs include the need to meditate, the importance of community and communal living, and the need to serve humanity selflessly (or 'seva'). Sikhism and the British Empire In total, there are around 26 million Sikhs worldwide, and over 24 million of these live in India. Outside of India, the largest Sikh populations are mostly found in former territories of the British Empire - the UK and Canada both have Sikh populations of over half a million people. Migration from India to other parts of the British Empire was high in the 19th century, due to the labor demands of relatively newer colonies, as well as those where slavery had been abolished. These countries also remain popular destinations for Sikh migrants today, as many are highly trained and English-speaking. Other regions with significant Sikh populations Italy also has a sizeable Sikh population, as many migrated there after serving there in the British Army during WWI, and they are now heavily represented in Italy's dairy industry. The Sikh population of Saudi Arabia is also reflective of the fact that the largest Indian diaspora in the world can now be found in the Middle East - this is due to the labor demands of the fossil fuel industries and their associated secondary industries, although a large share of Indians in this part of the world are there on a temporary basis.

In 2020, Indonesia recorded the largest population of Muslims worldwide, with around 239 million. This was followed with around 226.88 million Muslims in Pakistan and 213 million Muslims in India.

In 2020, around **** percent of the Iranian population identified as Muslim. Around ** percent identified as Shia Muslims in the same year, while a much smaller share followed the Sunni Muslim religion. In Iran, most Sunni Muslims belong to ethnic minority groups. Iran’s demographics The total population in Iran has grown steadily and is expected to surpass ** million in 2028. The vast majority of the population in the country was between 15 and 64 years of age. At the same time, the share of people aged above 64 increased in recent years and constituted over ***** percent of the total population. Muslim population worldwide In Europe, it was estimated that the Muslim population could triple by the middle of the century. In Southeast Asia, Indonesia had the largest share of Muslims as a proportion of its population. On the African continent, the highest number of Muslims was estimated in Nigeria, with close to a hundred million Islam followers. In the United States, less than one percent of the population identified as Muslims.

The two countries with the greatest shares of the world's Jewish population are the United States and Israel. The United States had been a hub of Jewish immigration since the nineteenth century, as Jewish people sought to escape persecution in Europe by emigrating across the Atlantic. The Jewish population in the U.S. is largely congregated in major urban areas, such as New York, Los Angeles, and Chicago, with the New York metropolitan area being the city with the second largest Jewish population worldwide, after Tel Aviv, Israel. Israel is the world's only officially Jewish state, having been founded in 1948 following the first Arab-Israeli War. While Jews had been emigrating to the holy lands since the nineteenth century, when they were controlled by the Ottoman Empire, immigration increased rapidly following the establishment of the state of Israel. Jewish communities in Eastern Europe who had survived the Holocaust saw Israel as a haven from persecution, while the state encouraged immigration from Jewish communities in other regions, notably the Middle East & North Africa. Smaller Jewish communities remain in Europe in countries such as France, the UK, and Germany, and in other countries which were hotspots for Jewish migration in the twentieth century, such as Canada and Argentina.

This statistic shows the top 25 countries in the world with the largest number of Hindu population in 2010. In 2010, there were about 974 million Hindus living in India.

According to a survey conducted in March 2025, almost 75 percent of Tinder users in the United States considered themselves religious, while 21 percent were non-religious.