Making the world better, one answer at a time. About 38 weeks, or 266 days. But really, any time between 250-280 days is a full term range (that's from conception... most dr's count from the first day of your last period- which is typically 14 days longer than the days I wrote). About 38 weeks, or 266 days. But really, any time between 250-280 days is a full term range (that's from conception...  About 38 weeks, or 266 days.