Pregnancy Calculator from Conception
Estimate your due date and current progress based on the exact day of conception.
How to Calculate Pregnancy from Conception Date
While most doctors calculate pregnancy based on the first day of your last menstrual period (LMP), many women know their exact date of conception—especially those tracking ovulation or undergoing IVF. Calculating from the date of conception is often considered more precise because it marks the actual biological start of the pregnancy.
Standard medical practice assumes a 280-day pregnancy from the LMP. However, human gestation actually lasts approximately 266 days (38 weeks) from the moment of conception. This calculator uses that 266-day rule to provide a highly accurate estimated due date (EDD).
The Math Behind the Calculation
To find your due date from conception, we apply the following logic:
- Due Date: Date of Conception + 266 days.
- Medical Gestational Age: Date of Conception + 14 days (to align with standard 40-week medical charts).
- Trimester Breakdown:
- First Trimester: Week 1 to Week 12.
- Second Trimester: Week 13 to Week 26.
- Third Trimester: Week 27 to Week 40.
Real-World Example
If you conceived on January 1st:
| Metric | Calculation | Result |
|---|---|---|
| Due Date | Jan 1 + 266 Days | September 24th |
| Medical Weeks | (LMP Equivalent) | 2 Weeks pregnant on Jan 1st |
Why Medical Professionals Use LMP Instead
Doctors typically use the First Day of your Last Menstrual Period because it is a definitive date that most patients remember. Since ovulation usually occurs 14 days after the start of a period, the "medical age" of a pregnancy is actually two weeks older than the "conception age." Our calculator automatically converts your conception date into the standard medical "Weeks Pregnant" format so you can stay in sync with your OB-GYN.
Is the Conception Date Accurate?
Even if you know the date you had intercourse, sperm can live inside the female reproductive tract for up to 5 days. Conception (the fertilization of the egg) may happen a few days after the actual event. However, this calculator remains the most accurate way to estimate timing without an early ultrasound.