Pregnancy Conception Calculator
About the Pregnancy Conception Calculator
Knowing your likely conception date can help you understand your pregnancy timeline better, especially for medical records or curiosity about when your baby was conceived.
Formula Used
How It Works
This calculator works backward from your due date, subtracting 266 days (38 weeks) - the average length of pregnancy counted from ovulation/conception.
Step by Step
- Start with your expected due date.
- Subtract 266 days (38 weeks), the average time from conception to birth.
- This gives your estimated conception date; subtracting 280 days instead gives your estimated LMP.
Worked Example
Example: Due date of 8 October:
Conception ≈ 8 October - 266 days = around 15 January
Frequently Asked Questions
Why 266 days and not 280?
280 days is counted from your last period, but conception itself typically happens about 2 weeks later, around ovulation, making the conception-to-birth span roughly 266 days.
Is this exact?
It's an estimate assuming a typical cycle - actual conception can vary by several days depending on your individual cycle.
Can this be used for legal purposes?
No, this is only a general estimate and not suitable for legal or medical paternity determinations.