How to Calculate Due Date

Calculating the Due Date

Generally speaking, calculating the due date is very easy and can be done in two different ways, namely: either by adding 266 days to the date of conception, or by adding 280 days (exactly 40 weeks) to the first day of the last menstrual period (LMP). However, unless the exact date of fertilization is known, counting from LMP is the common method of calculating the due date, and it is based on the assumption that fertilization in