1. How is Due Date Calculated from Ovulation?

The due date is calculated by adding 266 days (38 weeks) to the date of ovulation. This method is based on the typical gestation period from conception to birth.

2. Understanding the Calculation

The formula is simple:

This calculation assumes:

• Ovulation occurred on the specified date
• A standard gestation period of 266 days from conception
• No complications affecting pregnancy duration

3. Why 266 Days?

Details: The 266-day period (38 weeks) represents the average time from conception to birth. This differs from the common "40 weeks" calculation which is based on the first day of the last menstrual period (LMP).

4. Using the Calculator

Tips: Enter the exact date of ovulation for the most accurate due date estimation. If you're unsure of your ovulation date, other methods (like LMP-based calculation) may be more appropriate.

5. Frequently Asked Questions (FAQ)

Q1: How accurate is this calculation?
A: Very accurate if you know your exact ovulation date. Only about 5% of women deliver on their exact due date, but most deliver within 2 weeks before or after.

Q2: How does this differ from LMP-based due date?
A: LMP-based calculations add 280 days (40 weeks) to the first day of your last period, while ovulation-based adds 266 days (38 weeks) to ovulation.

Q3: What if I don't know my exact ovulation date?
A: If you tracked ovulation with temperature or tests, use that date. Otherwise, consider using an LMP-based calculator instead.

Q4: Does this work for IVF pregnancies?
A: Yes, for IVF using fresh embryos, ovulation/conception date is known precisely, making this method very accurate.

Q5: Why is my doctor using a different due date?
A: Doctors often use LMP-based dates unless you have precise ovulation data. Early ultrasound dating may also adjust the due date.