Conception Date Calculator
Curious about when your baby was conceived? Calculate the likely conception date based on your pregnancy information.
Calculate Conception Date
Find out when your baby was likely conceived based on your due date, last period, or ultrasound.
Enter the due date given by your healthcare provider.
How conception date is calculated: Conception typically occurs during ovulation, about 14 days after the first day of your last menstrual period. However, sperm can survive up to 5 days in the reproductive tract, so the actual conception window spans several days.
The most accurate way to determine conception is through early ultrasound measurements, as they can estimate gestational age within a few days.
How Conception Date Is Calculated
Conception occurs when a sperm fertilizes an egg, typically during ovulation. Since ovulation usually happens about 14 days after the first day of your last menstrual period (for a 28-day cycle), we can estimate the conception date by working backwards from your due date or forward from your LMP.
The Conception Window
Because sperm can survive in the female reproductive tract for up to 5 days, and an egg can be fertilized for about 12-24 hours after ovulation, there's actually a window of several days during which conception could have occurred.
- Sperm survival: Up to 5 days in the reproductive tract
- Egg viability: 12-24 hours after release
- Conception window: Approximately 6 days total
Calculation Methods
From Due Date
Conception is approximately 266 days (38 weeks) before your due date. This is the most common method used.
From Last Period
Conception typically occurs about 14 days after the first day of your last menstrual period.
From Ultrasound
Early ultrasound measurements can accurately date pregnancy, helping calculate the conception date more precisely.
Why Know the Conception Date?
- Curiosity: Many parents want to remember the special moment their baby was created
- Anniversary: Some couples mark the conception date as a meaningful date
- Paternity questions: In some cases, knowing the conception date helps clarify paternity
- Fun facts: Calculate your baby's zodiac sign and Chinese zodiac animal
Important Notes
- Conception date calculations are estimates and may not reflect the exact moment of fertilization
- Early ultrasound dating (before 14 weeks) is the most accurate method for determining gestational age
- Cycle length variations can affect the accuracy of LMP-based calculations
- For legal or medical purposes, consult with a healthcare provider