Ovulation varies
Even with regular cycles, ovulation can move by a few days from month to month. That shifts the likely conception date too.
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When was my baby conceived?
Estimate your conception date based on your due date or last menstrual period.
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Why it’s always an estimate
The fertile window
Conception usually happens within a day of ovulation, but sperm can survive for up to around five days — so intercourse several days earlier can lead to pregnancy.
From a due date
We count back 266 days (38 weeks) from your due date, which is the typical time from conception to birth.
FAQ
Questions parents ask
Can this calculator tell me the exact day I conceived?
No. It gives a likely window based on typical timing. The exact day usually can’t be known from dates alone.
Why does my scan date differ?
Scans measure your baby’s size, which can refine the estimate. If your provider has updated your due date, enter that date for the best estimate.
What if my cycles are irregular?
Irregular cycles make date-based estimates less reliable. A due date from an early scan is usually a better starting point.