Find your estimated conception date from your due date or LMP - and the fertile window when conception most likely occurred.
Conception = EDD − 266 days (38 weeks). A standard pregnancy lasts 280 days from LMP but 266 days from conception (ovulation/fertilisation).
Ovulation typically occurs at day 14 of a 28-day cycle. Conception = LMP + 14 days (±2 days depending on cycle length).
These are estimates. Ovulation can vary by 2–5 days and sperm can survive 3–5 days. An ultrasound-based EDD is more accurate than LMP alone.
Conception typically occurs 11 to 21 days after the first day of the last menstrual period (LMP), coinciding with the fertile window around ovulation. When a due date (estimated delivery date) is already known - from an ultrasound scan or from Naegele's rule (LMP + 280 days) - this tool works backwards to estimate the probable conception date and fertile window. Knowing the conception date can help parents understand the gestational timeline and align it with significant life events.
India's Pradhan Mantri Surakshit Matritva Abhiyan (PMSMA), launched in 2016, provides free antenatal check-ups to pregnant women on the 9th of every month at government health facilities. Under the scheme, the first trimester - weeks 1 to 13 - is identified as the most critical for screening and nutritional supplementation. An accurate conception date helps healthcare providers correctly date the pregnancy, schedule the first-trimester combined screening (NIPT or nuchal translucency scan at 11-13+6 weeks), and avoid mis-categorising gestational age. The National Health Mission (NHM) reports that early antenatal registration (before 12 weeks) significantly improves maternal and neonatal outcomes.