Pregnancy Conception Calculator

Trace back to the beginning of your journey

While most doctors focus on your due date, many parents are curious about exactly when they conceived. Because the precise moment of conception is rarely known, our calculator uses medical averages and your ovulation window to estimate the date your baby was created.

How Conception is Estimated

In a standard 28-day cycle, conception typically occurs about 2 weeks after the first day of your last menstrual period (LMP). However, because sperm can live inside the female reproductive tract for up to 5 days, the “conception window” is often broader than a single day.

The Calculation Methods:

1. From Due Date: Subtract 266 days (38 weeks) from your estimated due date.
2. From LMP: Add 14 days to the first day of your last period (assuming a 28-day cycle).
3. From Ultrasound: Use the gestational age provided by your doctor to count backward to “Week 2” of the pregnancy.

Understanding the “Conception Window”

It is a common misconception that conception happens immediately after intercourse. In reality, it can happen several days later.

• Sperm Longevity: Up to 5 days.
• Egg Viability: 12 to 24 hours after ovulation.
• The Window: Your most fertile days are usually the 3 days leading up to and including the day of ovulation.