Duration of Pregnancy

An average human pregnancy lasts for about 280 days or 40 weeks from the date of the last menstrual period (LMP). Traditionally, it has been calculated as 10 lunar months, or in terms of the modern calendar - 9 months and 7 days.

Fertilisation of the egg by the sperm, however, occurs (considering an average menstrual cycle of 28 days) 14 days after the last periods. Thus, the actual duration of a human pregnancy (gestation period) is 280 - 14 = 266 days.

Use our due date calculator to know your expected date of delivery.