Use an estimated due date to calculate a likely conception date and a small surrounding window. The result is an approximation because pregnancy dating does not usually identify one exact day of conception.
Conception Date Calculator
Use an estimated due date to calculate a likely conception date and surrounding window.
Conception cannot usually be pinpointed to one exact day without fertility-treatment records. The result is a practical estimate based on standard pregnancy dating conventions. See ACOG guidance on pregnancy dating.
Why conception is usually a window, not a single date
Pregnancy dating is normally expressed as gestational age, which starts from the LMP rather than the day fertilization occurred. Ovulation can shift, sperm can remain viable for several days, and the timing of fertilization and implantation is not directly observed in most spontaneous pregnancies.
How this calculator estimates conception
The central estimate is calculated approximately 266 days before the estimated due date, a standard relationship between conception-based timing and a 40-week LMP-based pregnancy. The tool displays a surrounding range to avoid false precision.
When the estimate can be more specific
Assisted reproductive technology can provide more precise dating information because the dates and developmental age of embryos are known. In those pregnancies, use the gestational age and due date assigned from treatment records.
