Conception calculator: when did I get pregnant?
Conception usually happens around ovulation, about 14 days before your next period. In a 28 day cycle that is around day 14. If you know your due date, conception was about 266 days (38 weeks) before it.
Enter a date to calculate.
Everything is calculated on your own device. We store nothing and send nothing anywhere.
This is an estimate, not medical advice and not contraception. If in doubt, ask your GP or midwife.
How we calculate
From your last period: first day plus your cycle length minus 14 days gives the likely ovulation. From your due date: 266 days back. Because sperm can survive up to 5 days, we also show the window in which conception was possible.
Why it is an estimate
Ovulation sometimes shifts by a few days, and the day of sex is not always the day of conception. A dating scan in the first trimester is more accurate than any calculator.
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Frequently asked questions
How do I know when I conceived?
Usually around ovulation: about 14 days before your next period. From your due date, count 266 days back.
Can sex a few days before ovulation lead to pregnancy?
Yes. Sperm can survive up to 5 days, so sex in the 5 days before ovulation can lead to a pregnancy.
My scan gives a different date, which is right?
Follow the scan. It measures the size of your baby and is more accurate than counting from your period.
Can this prove who the father is?
No. A calculation only gives a window of a few days. That needs a DNA test.
Read more
Other free tools
Sources: NHS, Periods and fertility in the menstrual cycle; NHS, Pregnancy due date; ACOG, Methods for estimating the due date.