Pregnancy Due Date Calculator
Estimate an expected due date from the first day of the last menstrual period. The calculator also displays estimated pregnancy week and day, approximate trimester, estimated conception date and the number of days remaining until the estimated due date. Pregnancy dating is an estimate and may be changed by ultrasound or clinical assessment.
How to use the Pregnancy Due Date Calculator
- Enter the first day of the last menstrual period.
- Enter the usual menstrual cycle length.
- The standard pregnancy estimate begins with 280 days from the first day of the last menstrual period.
- The calculator adjusts the estimate by the difference between the entered cycle length and 28 days.
- Pregnancy week and day are calculated from the resulting estimated due date.
- The countdown shows days remaining, the due date itself, or days past the estimated due date.
Examples
Standard 28-day cycle
For a 28-day cycle, the basic calculation estimates the due date 280 days after the first day of the last menstrual period.
Pregnancy countdown
If the estimated due date is 80 calendar days away, the calculator displays approximately 80 days remaining.
Frequently asked questions
How is a pregnancy due date estimated?
A conventional estimate is 280 days, or 40 weeks, from the first day of the last menstrual period.
Does the calculator show how many days are left?
Yes. It calculates the calendar difference between today and the estimated due date.
Does it show the pregnancy week?
Yes. It displays an estimated gestational week and additional days.
Is the estimated conception date exact?
No. It is a calendar estimate and should not be interpreted as proof of the actual conception date.
Can ultrasound change the due date?
Yes. Clinical dating, particularly early ultrasound, may produce a different estimate.
What if the estimated due date has already passed?
The calculator displays the number of calendar days past the estimated due date. Medical decisions about a pregnancy should be discussed with a healthcare professional.
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