🤰 Conception Date Calculator
Estimate your likely conception date and due date based on the first day of your last menstrual period and your average cycle length.
How conception date is estimated
Ovulation, and therefore likely conception, typically occurs about 14 days before the next period begins. This calculator takes the first day of your last menstrual period (LMP), adds (cycle length – 14) days to estimate the ovulation/conception window, and separately adds the standard 280 days (40 weeks) to the LMP to estimate a due date using Naegele’s rule.
Why it’s an estimate
Actual ovulation timing varies between individuals and even between cycles for the same person, especially with irregular cycles. This calculator assumes a fairly typical cycle pattern and a luteal phase (time between ovulation and the next period) of about 14 days, which is common but not universal.
This tool provides a general estimate for educational and planning purposes only. For a more precise estimate, an early ultrasound or clinical evaluation from a healthcare provider is more accurate than calendar-based methods alone.