Due Date Calculator
Estimate your due date from your last period, plus how far along you are right now.
PregnancyScience-backed formula
Enter your details
Fill in the fields, then calculate
Please choose a date.
Enter your cycle length.
Awaiting Data
Enter your details and tap Calculate to see your results appear here.
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ResultYour result appears here.
How the Due Date Is Found
The common method, Naegele's rule, adds 280 days to the first day of your last period. That marks 40 weeks, the typical length of pregnancy.
Key dates line up into an easy week by week timeline.
A cycle longer or shorter than 28 days shifts the date a little, so the tool adjusts for it.
Only about one baby in twenty arrives on the exact date. Treat it as a target window.
How to Use This Calculator
- Choose the first day of your last period.
- Adjust your cycle length if needed.
- Tap Calculate for your due date and progress.
The Formula Used
Due date = last period + 280 days + (cycle − 28)
- last period
- First day of your last menstrual period.
- cycle
- Your average cycle length.
Understanding Your Results
First trimester
Weeks 1 to 12
Early growth and development.
Second trimester
Weeks 13 to 26
Often the most comfortable phase.
Third trimester
Weeks 27 to 40
Final growth before birth.
Tips to Improve
- Confirm dates with an early ultrasound.
- Track symptoms week by week.
- Keep regular prenatal appointments.
- Ask your provider any questions early.
Frequently Asked Questions
It is an estimate. Only about five percent of babies arrive on the exact day.
An ultrasound gives a more reliable date than the last-period method.
Yes. Early scans often refine it within the first trimester.
Scientific References
- American College of Obstetricians and Gynecologists. (2017). Methods for estimating the due date. Committee Opinion No. 700.
- Naegele, F. K. (1812). Lehrbuch der Geburtshilfe.
- Jukic, A. M., et al. (2013). Length of human pregnancy. Human Reproduction, 28(10), 2848–2855.