The U.S. government estimates the total population at 67.4 million (July 2018 estimate).  According to the most recent study by the National Institute for Demographic and Economic Studies, conducted in 2008 and published in 2010, 45 percent of respondents aged 18-50 reported no religious affiliation, while 43 percent identified as Roman Catholic, 8 percent as Muslim, 2 percent as Protestant, and the remaining 2 percent as Orthodox Christian, Buddhist, Jewish, or other.

A poll conducted in March by the private firm Opinionway found 41 percent of respondents older than 18 years identify as Catholic, 8 percent Muslim, 3 percent Protestant, 1 percent Buddhist, and 1 percent Jewish; 43 percent said they have no religious affiliation.

According to a survey conducted in March by the Catholic Institute of Paris and St. Mary’s Catholic University in the United Kingdom, 64 percent of young people aged 16-29 in France declared themselves without a religion compared with 23 percent who said they were Catholic and 10 percent who said they were Muslim.

The MOI estimates 8-10 percent of the population is Muslim.  The Muslim population consists primarily of immigrants from former French colonies in North and sub-Saharan Africa and their descendants.  According to a Pew Research Center study published in November 2017, Muslims number 5.72 million, 8.8 percent of the total population.

According to a 2017 Ipsos study published in Reforme, a Protestant online news daily, there are an estimated 600,000 Lutheran, 600,000 evangelical, and 800,000 nondenominational members in the Protestant community.  Many evangelical churches primarily serve African and Caribbean immigrants.

A 2016 report by Berman Jewish Data Bank estimated there are 460,000-700,000 Jews, depending on the criteria chosen.  According to the study, there are more Sephardic than Ashkenazi Jews.

The Buddhist Union of France estimates there are one million Buddhists, mainly Chinese and Vietnamese immigrants and their descendants.  Other religious groups estimate their numbers as follows:  Jehovah’s Witnesses, 120,000; Orthodox Christians, most of whom are associated with the Greek or Russian Orthodox Churches, 80,000-100,000; The Church of Jesus Christ of Latter-day Saints, 66,000; Church of Scientology, 45,000; and Sikhs, 30,000.