Estimate when you likely conceived, from a due date or your last period.
Estimate only - not medical advice. Ovulation and conception timing vary by cycle.
You can estimate conception from a due date or from your last menstrual period. Both methods use the same underlying biology.
From a due date: a full-term pregnancy lasts about 266 days from conception (around 38 weeks), so we count back 266 days from the due date to land on an estimated conception date.
From your last period (LMP): due dates are usually measured from the first day of the last menstrual period, which is about two weeks before conception. In a typical 28-day cycle, ovulation and conception happen around day 14, so we add about 14 days to your LMP.
Cycles vary, so we also show a likely range of roughly plus or minus 5 days. If your cycle is shorter or longer than 28 days, or if ovulation came early or late, the real conception date can shift within or beyond that window.
Once you have an estimate, use our due date and pregnancy calculators to track next steps.
From a due date we count back 266 days. From the first day of your last period we add about 14 days, which is roughly when ovulation happens in an average 28-day cycle.
No. It gives a best estimate plus a likely range of about plus or minus 5 days, because ovulation and fertilization timing vary from person to person and cycle to cycle.
Yes. Ovulation can fall earlier or later than day 14 if your cycle is shorter or longer than 28 days, which shifts the estimated conception date.
Conception is when the egg is fertilized. Implantation, when the embryo attaches to the lining of the uterus, usually happens about 6 to 10 days later.
No. Results are estimates for general information only. An early ultrasound and your doctor or midwife give the most accurate dating.