The Pregnancy Due Date Calculator estimates the fertility window, date of conception, gestational age and due date based on the first day of last menstrual period and average cycle length. The calculations provided are just estimates based on averages and can not substitute professional diagnosis.
Pregnancy due date estimator
Estimated Fertility Window
According to clinical guidelines, the fertility window of the average woman is between days 10 and 17 of her menstrual cycle on the assumption that ovulation occurs exactly 14 days before the next cycle begins. Still the timing of the fertility window is highly variable even in women with regular menstrual cycle, and for most women it is beyond the specified interval. The window depends also on the cycle length. Women with their cycles lasted less on average ovulate earlier and therefore have earlier fertile windows than women with longer cycles.
Estimated Conception Date
Most women don’t know the exact conception date because they usually don’t know exactly when ovulation occurs. For a woman with a regular 28-day period, ovulation often occurs on or around day 14 and, thus, conception occurs typically about 11-21 days after the first day of the last period. So the assumption, used in this calculator, that their conception occurs around mid-cycle is an acceptable estimate based on the first day of their last period. But in case of irregular cycles, other methods are used to determine conception dates.
Estimated Gestational Age
Gestational age (or menstrual age), is a clinical term describing embryonic development timed from the first day of the last menstrual period and expressed in weeks and days. In case of a cycle that is not a 28-day cycle the gestational age is estimated by adding 14 days to the time span from the estimated conception date.
Estimated Due Date
The due date (or delivery date) can be estimated by adding 280 days to the first day of the last menstrual period. In case of a cycle that is not a 28-day cycle the due date is estimated by adding 265 days to the estimated conception date.
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Disclaimer. Please remember that this calculator is intended for education use only. It is not intended to replace the medical advice of your doctor or healthcare provider. Please consult your doctor for advice about your specific medical condition.