how long does it take to spawn a NPC in terraria

Answer 1

It depends on the time of day inside the game.

If its daytime it will usually will have 1 NPC every 2 Minutes.

If its night time the NPCs will not spawn.

However it also affects if a bloodmoon has happened. If a Bloodmoon has occured the NPC will not spawn for the first 10 minutes of the day after.

Officially Day starts 4:30 game time

Hope that helps.