Pregnancy Conception Calculator
Estimate a likely conception date and possible fertile window from a last menstrual period, due date, or IVF embryo-transfer date.
Choose your method
A cycle adjustment is an estimate; ovulation can vary.
Your estimate
Estimated conception date
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How the conception estimate works
Pregnancy is conventionally dated from the first day of the last menstrual period, about two weeks before conception in a typical 28-day cycle. From an estimated due date, this tool counts back about 266 days. For IVF, it accounts for whether the embryo was transferred on day 3 or day 5.
Why the actual date may differ
- Ovulation may not occur on the same cycle day every month.
- Cycle length does not perfectly predict ovulation.
- Implantation occurs after fertilization, not at the same moment.
- Ultrasound dating may lead a clinician to revise the estimated due date.
Frequently asked questions
Is conception the same as intercourse?
No. Fertilization can occur days after intercourse because sperm can survive in the reproductive tract for several days.
Is conception the same as implantation?
No. Conception generally refers to fertilization; implantation occurs later when the developing embryo attaches to the uterine lining.
Can this calculator confirm paternity?
No. Date estimates cannot establish paternity. Only appropriate genetic testing can do that.
Which method is most accurate?
A known IVF transfer date is usually more specific than an LMP estimate. Clinical ultrasound and your healthcare professional’s assessment should guide pregnancy dating.
Medical notice
This calculator provides general educational estimates and does not confirm pregnancy, conception, viability, gestational age, or paternity. Seek medical advice for pregnancy concerns, pain, bleeding, unusual symptoms, or uncertainty about dates.
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