Pregnancy Conception Date Calculator – Estimate When You Conceived
Estimate your conception date from your expected due date. Conception is approximately 266 days (38 weeks) before the due date. Enter your due date to get the estimated conception date.
Pregnancy Conception Date Calculator
Estimate conception date from your due date. Conception is approximately 266 days (38 weeks) before the due date.
How the formula works
Conception date = Due date − 266 days
The due date is typically 280 days from the last menstrual period (LMP). Ovulation and conception occur around day 14, so from conception to due date is 280 − 14 = 266 days.
Understanding conception and due dates
Pregnancy dating can be confusing because clinicians often use the last menstrual period (LMP) as the starting point, even though conception happens about two weeks later. The due date is calculated as LMP + 280 days (40 weeks). Conception typically occurs at ovulation, around day 14 of a 28-day cycle, so from conception to due date is 266 days. This calculator reverses that: given your due date, it subtracts 266 days to estimate when conception likely occurred.
Knowing your conception date can help with prenatal planning and understanding fetal development milestones. It is also useful if you need to recall the timing of conception for medical or personal reasons. Keep in mind that ovulation can vary by several days, and sperm can survive up to five days in the reproductive tract, so the actual conception window may span a few days. This tool provides an estimate, not a definitive date. For clinical decisions, always follow your healthcare provider's guidance.