Conception Date Estimation from Due Date: July 29 Example

To estimate conception from a due date, subtract 266 days (38 weeks embryonic gestation).

Calculation

• Due date: July 29, 2023 (assuming current year).
• July 29 − 266 days = November 14, 2022.

Alternative: From LMP

If LMP known: Conception ≈ LMP + 14 days. Due date = LMP + 280 days.

Precision Notes

• Actual conception window: ±3–5 days around ovulation.
• Early ultrasound (CRL) is more accurate than date math.
• Cycle length shifts ovulation date.

Use this for rough planning only; confirm with prenatal provider.