Pregnancy Conception Calculator
Estimate conception date from LMP, due date, or gestational age. Includes ovulation estimate, fertile window, and due date confirmation.
How conception date is estimated
This calculator estimates a likely conception date using common pregnancy dating conventions. In clinical practice, pregnancy is usually dated from the first day of the last menstrual period (LMP), which is typically about two weeks before ovulation and conception in a 28-day cycle.
Using the LMP method, the estimated due date (EDD) is calculated as 280 days (40 weeks) from LMP. A conception estimate is often calculated as 266 days (38 weeks) before the due date. Ovulation timing can vary, especially with irregular cycles, so this tool also provides an optional cycle-length-based ovulation estimate.
LMP vs ovulation vs conception
Last menstrual period (LMP) is the standard baseline used to count pregnancy weeks. Ovulation typically occurs about 14 days before the next period (day 14 in a 28-day cycle). Conception usually occurs close to ovulation, but exact timing can differ.
Fertile window and ovulation timing
The fertile window is commonly estimated as the 5 days before ovulation through about 1 day after ovulation. These dates are approximate and should be treated as general guidance, not a guarantee of fertility or conception timing.
FAQ
Questions people ask
How do you estimate conception date?
A common estimate is 266 days (38 weeks) before the due date. Another estimate uses ovulation timing based on cycle length.
Is conception date the same as ovulation date?
Conception often occurs close to ovulation, usually within about 24 hours, but timing can vary.
Can I calculate conception date from due date?
Yes. Conception is often estimated as due date minus 266 days, and LMP is estimated as due date minus 280 days.
How many days after my period did I conceive?
In a 28-day cycle, ovulation often occurs around day 14. With other cycle lengths, ovulation may occur earlier or later.
Is this conception calculator accurate?
It provides an estimate. Ovulation and implantation vary between individuals, and clinical dating may be revised by ultrasound.
Disclaimer
This calculator is for informational purposes only and does not provide medical advice. For personalized guidance, consult a qualified healthcare professional.