Where the traditions land

Population figures are each tradition's own most recent published count. Eligibility is set against the World Christian Database, the standard reference for global denominational data.

Why the disagreement

This question sounds like it should have one factual answer, but the count changes depending on which ancient list of authoritative books a tradition inherited — Christianity never had one single moment where every branch of the church agreed on a final list at the same time.

Catholic and Oriental Orthodox teaching count 73 books: the 39 Old Testament books found in every Christian Bible, plus seven more — Tobit, Judith, Wisdom, Sirach, Baruch, and 1–2 Maccabees, along with additions to Esther and Daniel — drawn from the Septuagint, the Greek Old Testament used by the earliest Christians and quoted throughout the New Testament. Catholic teaching formally closed this list at the Council of Trent in 1546, specifically in response to the Reformation's rejection of these books. Oriental Orthodox teaching, sourced here to the Coptic Orthodox Church specifically, reaches the same 73-book total through its own textual tradition; other Oriental Orthodox bodies aren't uniform on this — the Ethiopian Orthodox Tewahedo Church, a related but separate Oriental Orthodox body, holds a considerably broader canon of its own, running as high as 81 books.

Eastern Orthodox teaching counts still more: the same Septuagint-based list Catholic and Coptic teaching use, plus additional books — 3 Maccabees, 1 Esdras, and the Prayer of Manasseh among them — that never made it into the Catholic list, bringing the commonly cited Orthodox Old Testament to 49 books and the total to 76. As with other Eastern Orthodox questions in this format, no single document binds every autocephalous church to one final number; individual jurisdictions vary in exactly which books they append and how they're counted.

Anglican, Lutheran, Reformed, Methodist, Southern Baptist, Pentecostal, Adventist, and Jehovah's Witness teaching all count 66: the 39 Old Testament books recognized by the Hebrew canon, plus the 27 New Testament books every Christian tradition agrees on, with the Trent-era additions excluded from Scripture proper. That number is shared, but what to do with the excluded books isn't. Anglican and Lutheran teaching retain them in a secondary tier — printed and read, in Anglican language, "for example of life," but never used "to establish any doctrine"; Luther's own Bible carried nearly identical language, calling them "not held equal to Holy Scripture" but still "useful and good to read." Reformed teaching rejects them outright: the Westminster Confession calls them "no part of the Canon of Scripture," carrying "no authority in the Church of God," to be treated as ordinary human writing. Methodist, Southern Baptist, Pentecostal, Adventist, and Jehovah's Witness teaching don't engage the excluded books at all in their core statements of faith — the 66-book Bible is simply the whole of Scripture, with nothing set aside as secondary reading.

LDS teaching also lands on 66 books for the Bible specifically, using the King James Version — with a qualification no other seated tradition makes. Its own eighth Article of Faith states belief in the Bible "as far as it is translated correctly," leaving open that any given passage may not be, and the Bible isn't LDS teaching's only book of scripture: the Book of Mormon, Doctrine and Covenants, and Pearl of Great Price stand alongside it as equally authoritative "standard works." Sixty-six answers the question asked, without answering what LDS teaching treats as the complete body of scripture.

Solving the disagreement

Catholic, Oriental Orthodox, Eastern Orthodox, and the 66-book traditions are arguing, underneath the specific lists, about which ancient community's judgment should govern the question at all: the Hebrew canon settled by rabbinic Judaism after Christianity had already split off, or the broader Greek Septuagint that Jesus and the apostles are quoted using throughout the New Testament. Both sides can point to real historical evidence — early Christian writers who used the wider list liturgically, and early Christian writers, including Jerome, who argued the wider list shouldn't be treated as fully canonical even while living in a church that read from it. That's not a gap better manuscript evidence is likely to close, because the two sides aren't just weighing the same evidence differently — they're applying different rules for what counts as evidence of canonicity in the first place: continuous ecclesiastical usage, or the judgment of the specific community that produced the texts.

Anglican and Lutheran teaching sit closer to a genuine middle position than a resolvable dispute. Both traditions already do what Reformed teaching asks for in substance — treat the extra books as non-doctrinal — while keeping them in circulation for the reason Jerome himself gave them: moral instruction. The live disagreement inside the 66-book bucket is narrower than it looks: whether a middle tier between "Scripture" and "not worth reading" is coherent at all, or whether Reformed teaching's harder line — no such tier exists — is the more consistent application of the same Reformation-era logic everyone in that bucket otherwise shares.

LDS teaching's addition is a different kind of fork, one this format keeps running into: whether authoritative revelation continued after the New Testament closed. Nothing about textual history settles that question either way — it depends on whether continuing revelation is possible at all, a premise the historical evidence for any specific book can't adjudicate.

Sources

Same standing source per tradition on every post, not hunted per question.

• Catholic — Catechism of the Catholic Church
• Eastern Orthodox — Nicene-Constantinopolitan Creed (binding across all jurisdictions); The Longer Catechism of St. Philaret of Moscow (widely used, not binding on every jurisdiction)
• Oriental Orthodox — Catechism of the Coptic Orthodox Church, Fr. Tadros Y. Malaty (Amazon — no full free text found)
• Anglican — Thirty-Nine Articles of Religion
• Lutheran — Book of Concord
• Reformed/Presbyterian — Westminster Confession of Faith
• Methodist/Wesleyan — Articles of Religion
• Southern Baptist Convention — Baptist Faith & Message 2000
• Pentecostal (Trinitarian) — Assemblies of God Statement of Fundamental Truths
• Seventh-day Adventist — 28 Fundamental Beliefs
• LDS — Book of Mormon and Doctrine and Covenants
• Jehovah's Witnesses — What Does the Bible Really Teach?