The U.S. government estimates the total population at 28.1 million (July 2016 estimate), including more than eight million foreign residents. Between 85 and 90 percent of the approximately 20 million citizens are Sunni Muslims who predominantly adhere to the Hanbali School of Islamic jurisprudence.

Shia Muslims constitute 10 to 15 percent of the citizen population. Approximately 80 percent of Shia are “Twelvers” (followers of Muhammad ibn Hasan al-Mahdi, whom they recognize as the Twelfth Imam) and are primarily located in the Eastern Province. Nakhawala, or “Medina Shia,” are also Twelvers and reside in small numbers in the western Hejaz region. Estimates place their numbers at approximately 1,000. Twelver Shia adhere to the Jafari School of jurisprudence. Most of the remaining Shia are Sulaimani Ismailis, also known as “Seveners” (those who branched off from the Twelvers to follow Isma’il ibn Jafar as the Seventh Imam). Seveners number approximately 700,000 and reside primarily in Najran Province, where they are the majority of the province’s inhabitants. Another branch of Sevener Shia, the Bohra Ismailis, number approximately 1,000, the majority of whom are South Asian expatriates who reside in the western Hejaz region. Pockets of Zaydis, another offshoot of Shia Islam, number approximately 20,000 and reside primarily in the provinces of Jizan and Najran along the border with Yemen.

Foreign embassies indicate the foreign population in the country, including many undocumented migrants, may exceed 10 million, most of whom are Muslim. According to a 2010 survey by the Pew Research Center, out of the country’s total population (including foreigners), there were approximately 25.5 million Muslims, 1.2 million Christians (including Eastern Orthodox, Protestants, and Roman Catholics); 310,000 Hindus; 180,000 religiously unaffiliated (including atheists, agnostics, and people who did not identify with any particular religion); 90,000 Buddhists; 70,000 followers of folk religions; and 70,000 followers of other religions.