Pregnancy Conception Calculator

How the calculation works

Conception usually happens about 266 days before the due date, which is about two weeks after the start of the last period. The fertile window runs from five days before ovulation to one day after.

Formula used

Conception date = due date − 266 days; Last period = due date − 280 days

Example

A due date of 14 May 2027 points to conception around 21 August 2026.