How does a Conception Calculator work?
While Due Date calculators work forwards to predict when a baby will be born, a Conception Calculator works backwards. It takes medical data (like your doctor-provided Estimated Due Date or an early ultrasound scan) and subtracts standard gestational timelines to find the moment the egg was fertilized.
Understanding the Conception Timeline
A standard pregnancy is calculated as 280 days (40 weeks) from the First Day of the Last Menstrual Period (LMP). However, conception does not happen on the day of the LMP. It happens at ovulation, which is typically 14 days after the LMP. Therefore, the actual moment of conception is medically considered to be exactly 266 days before your Due Date.
Why is there an "Intercourse Window"?
You do not necessarily have to have intercourse on the exact day of conception to get pregnant. This is because of human biology:
- Sperm Lifespan: Sperm can survive inside the female reproductive tract for up to 5 days waiting for an egg to be released.
- Egg Lifespan: Once released (ovulation), an egg only survives for 12 to 24 hours.
Because of this, if your conception date was the 15th of the month, intercourse that occurred anywhere between the 10th and the 16th could have resulted in the pregnancy.
Disclaimer: Unless conception occurred via IVF (In Vitro Fertilization), it is impossible to determine the exact minute or hour of conception. This calculator provides the most mathematically accurate biological window based on clinical standards.