Understanding Your Conception Date

Your conception date is the day on which the sperm fertilized the egg. This event happens during ovulation, which is a small window of time each month. While pinpointing the exact moment can be difficult without medical tracking, this calculator provides a highly accurate estimation based on the most common calculation methods used by healthcare professionals.

The Fertility Window: More Than Just One Day

Conception can only occur during your "fertility window." This critical period includes the day of ovulation and the five days leading up to it. This is because sperm can survive in the female reproductive tract for up to five days, waiting for the egg, which is viable for about 12-24 hours after being released. This calculator estimates this 6-day window to give you a complete picture of when conception was possible.

How The Calculator Works

Our calculator uses two different methods to estimate your date of conception:

• From Last Menstrual Period (LMP): This is the most common method. It assumes ovulation happens about 14 days *before* the start of your next period. By providing your LMP date and your average cycle length, we can predict your ovulation date and therefore your most likely conception date.
• From Due Date: If you've been given a due date from your doctor (often confirmed by an ultrasound), this is a very reliable method. A full-term pregnancy is considered 266 days (or 38 weeks) from the date of conception. This calculator simply works backward from your due date to find when you most likely conceived.

Once you know your likely conception and LMP dates, you can explore our full Pregnancy Calculator for a complete week-by-week timeline and key trimester milestones.

A healthy pregnancy starts with a healthy you. Your pre-pregnancy health, which can be initially assessed with a BMI calculation, plays an important role in fetal development.

Disclaimer: This tool provides an estimate for informational purposes and is not a substitute for professional medical advice. The dates provided are based on statistical averages. An ultrasound performed by a healthcare professional is the most accurate way to determine gestational age and confirm dates.