Acts 4:4

Belief was the key factor in many more becoming Christians (cf. Acts 3:19), not believing and being baptized (Acts 2:38). Note that Luke wrote that they "believed" the message they had heard. The total number of male converts in Jerusalem now reached 5,000 (cf. Acts 1:15; Acts 2:41) because of Peter’s message. The Greek word andron specifies males rather than people. Normally most of the people in the temple courtyard who would have witnessed these events would have been males. Estimates of Jerusalem’s total population range from 25,000 to 250,000, though the lower figure seems more probable. [Note: Marshall, The Acts . . ., pp. 98-99.] One writer argued for 60,000 or more inhabitants. [Note: Fiensy, p. 214.] Another believed 100,000 to 120,000 people inhabited the city in the forties. [Note: Wolfgang Reinhardt, "The Population Size of Jerusalem and the Numerical Growth of the Jerusalem Church," in The Book of Acts in Its First Century Setting; Vol. 4: The Book of Acts in Its Palestinian Setting, p. 263.] Obviously there is a wide range of speculation.