Distribution of Eastern Orthodox Christians in the world by country:
Main religion (more than 75%)
Main religion (50–75%)
Important minority religion (20–50%)
Important minority religion (5–20%)
Minority religion (1–5%)
Tiny minority religion (below 1%), but has local autocephaly
Based on the numbers of adherents, Orthodoxy is the second largest Christian communion in the world after the Roman Catholic Church. The most common estimates of the number of Orthodox Christians worldwide is approximately 225–300 million. The numerous Protestant groups in the world, if taken all together, outnumber the Orthodox, but they differ theologically and do not form a single communion.
Ancient Eastern Orthodox communities still have large populations in countries such as Lebanon, Israel and Palestine (Jerusalem and Bethlehem). Large Orthodox communities with ancient histories have been completely removed from some of their ancestral homes and therefore no longer have a presence in those locations, specifically Anatolia and Cappadocia.
The number of members of the Orthodox Church in each country has been subject to a lot of debate. Each study performed that seeks to discover the number of adherents in a country may use different criteria, and be submitted to different populations. As such, some numbers may be inflated, and therefore inaccurate. Examples of this are Greece and Russia, where estimates of adherence to Orthodoxy may reach 80-98%, but where additional studies find that only 70-80% of the population are confident in a belief in God. The likely reason for this disparity is that many people in these majority Orthodox countries will culturally identify with the Orthodox Church, especially if they were baptized as children. This includes those who may be irreligious, yet culturally identify with the Orthodox Church, or for whom Orthodox Christianity is listed on official state records. Other cases of incongruent data also might be due to counting ethnic groups from Orthodox countries rather than actual adherents. A case of this is the United States, which has large numbers of immigrants from Orthodox countries. The variety of Orthodox jurisdictions often reported large numbers of members, which together would total 2-3 million across the country. However, a 2010 study by Alexei Krindatch sought data from each parish, with the specific criteria of annual participation. This extensive study produced the "Atlas of American Orthodox Christian Churches", and discovered that despite previously inflated numbers of several million, there were only about 817,000 Eastern Orthodox Christians (including traditions not recognized by mainstream organizations) in the United States. The study explained that such a difference was due to a variety of circumstances, including the counting of ethnic populations who might have immigrated from Orthodox countries, or who might have ancestry from such countries. This study, while initially controversial, proved groundbreaking, and has since been officially approved for use by the Assembly of Canonical Orthodox Bishops of North and Central America.
As such, any data used to figure the population of Orthodox per nation, should be understood as estimated rather than exact. Additionally, total numbers of Orthodox Christians throughout the world may be anywhere from 150 million to 300 million, depending on the studies and definitions which are used.
^Data is estimated, Greece is said to be 98% Orthodox, but additional studies found only 60-80% believe in God, if true, then no more than 80% may be Orthodox.
^Data is estimated, studies list Russia's population between 40% & 90% Orthodox. Studies have also found between 60% & 70% believe in God. If true, then no more than 70% can be Orthodox as such requires a belief in God.
^Almost half the population of Greece is under the jurisdiction of Constantinople, this church also has half a million members in the United States, half a million in Guatemala and under half a million in Australia. Some estimates put crypto-membership in Turkey in the millions, but that is unconfirmed.
^Jay Diamond, Larry. Plattner, Marc F. and Costopoulos, Philip J. World Religions and Democracy. 2005, page 119.(also in PDF file[dead link], p49), saying "Not only do Protestants presently constitute 13 percent of the world's population—about 800 million people—but since 1900 Protestantism has spread rapidly in Africa, Asia, and Latin America."