The mustard seed.

How Christianity grew from a handful of followers to about 2.7 billion people, compared with other fast-growing movements. The first three centuries are known only from models, and modern growth from counts.

Reach map Scripture translation Growth

Measured 4Model 1Estimate 1Projection tested 1Finding 1

The first three centuries: members by years since founding

Early Christians (Stark's model)Latter-day Saints (records)

Years since founding on the horizontal axis (Christianity counted from 30 CE, the Latter-day Saints from 6 April 1830). Christianity: Rodney Stark's model, 1,000 members in 40 CE growing 40% a decade (The Rise of Christianity, 1996), not counts. Latter-day Saints: the church's own membership records. On a log scale, a steady growth rate is a straight line.

1,000 to 33.9 million

Christians, 40-350 CE

Stark models 1,000 Christians in 40 CE growing 40% a decade to about 6.3 million by 300 and a majority of the empire by 350.

Model

about 6 million (about 10% of the empire)

Christians around 300 CE

Scholars put Christians at about a tenth of a Roman Empire of about 60 million by around 300 CE.

Estimate

6 to 17.9 million

Latter-day Saints, 1830-2025

From six founding members in 1830 to 17.9 million in 2025, about 43% a decade between 1850 and 1990.

Measured

64 to 267 million by 2080

Stark's 1984 projection of Latter-day Saint growth

Stark projected 64-267 million by 2080. Membership was near his high line in 2010 and near the low line by 2025, as growth slowed from about 5% a year to 1-2%.

Projection tested

558 million to 2.66 billion

Christians worldwide, 1900-2025

Christians grew nearly fivefold in 125 years but held a steady third of the world: 34.5% in 1900, 32.5% in 2025.

Measured

200 million to 2.07 billion

Muslims worldwide, 1900-2025

Muslims grew about tenfold, from about an eighth of the world to about a quarter.

Measured

about 1 million to 704 million

Pentecostals and Charismatics, 1900-2025

The renewal movement grew from under a million to about 700 million, the fastest-growing part of Christianity.

Measured

Is early Christian growth unusual?

A 40%-a-decade rate is high but not unique: a modern movement sustained it for over a century under ordinary conditions.

Finding

← All figures

Latter-day Saints, 1830-2025

GradeMeasured

Value: 6 to 17.9 million
Source: LDS Church records

The Christian case

The growth of the Church of Jesus Christ of Latter-day Saints, set out in the church's own records, gives a well-documented modern comparison for the early church's growth. From six founding members on 6 April 1830, membership reached 51,839 by 1850, 1,111,314 by 1950, 11,068,861 by 2000 and 17,887,212 by 2025. Between 1850 and 1990 it grew by about 43% a decade, the same rate Stark estimated for early Christianity, as Ehrman also observes. For those who study the early church, this shows that Stark's picture is realistic: a committed, missionary community really can grow from a small start to millions at that pace, so the early church's spread from a few believers to millions is historically credible.

What the research found

Measured: these are the church's records of baptised members, year by year. Growth averaged about 43% a decade from 1850 to 1990 (from 51,839 to 7,761,179 over fourteen decades). Since then it has slowed, to between about 0.6% and 2% a year in 2020-2025.

Explore the counterarguments

The records count baptised members, including those no longer active, so they measure affiliation rather than practice. One 2024 count of observed weekly attendance in the United States put it at about 14-15%, against 76% of members who report attending monthly. A movement can sustain a high growth rate for well over a century and then slow sharply, so a long run of fast growth does not by itself show where a movement is heading.