Christianity in the roman empire.

[Epictetus]

In regards to when exactly the Roman Empire became majority Christian, I decided to check and see what Gibbon had to say. Gibbon estimates that only 20% of the population was Christian by the time of Constantine. Like others have mentioned, he also points out that some regions and cities had a much higher proportion of Christians than others (Near East vs. Gaul, for instance).

It looks like he thinks that the Empire was majority Christian by about a generation after Theodosius – say about 420 or so.