Due Date Calculator
Estimate your baby's due date based on your last menstrual period (LMP) or conception date.
Estimated Due Date
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Gestational Age Today
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Conception Date (est.)
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End of First Trimester
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End of Second Trimester
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Days Remaining
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How to Use the Due Date Calculator
- Choose your method: Select LMP (last menstrual period) or conception date.
- Enter the date: Provide the first day of your last period or your conception date.
- Adjust cycle length: If using LMP, enter your average cycle length (default is 28 days).
- View your results: See your estimated due date, gestational age, and trimester milestones.
How Due Date is Calculated
The due date is estimated using Naegele's rule:
- From LMP: Add 280 days (40 weeks) to the first day of your last period, adjusted for cycle length.
- From Conception: Add 266 days (38 weeks) to the conception date.
Frequently Asked Questions
How accurate is a due date calculator?
Only about 5% of babies are born on their exact due date. Most babies arrive within two weeks before or after the estimated date. An ultrasound in the first trimester provides the most accurate dating.
What if my cycle is irregular?
If your cycle is irregular, the LMP method may be less accurate. An early ultrasound is recommended for more accurate dating. You can also use the conception date method if you know when conception occurred.
What are the trimesters?
The first trimester spans weeks 1-12, the second trimester covers weeks 13-26, and the third trimester runs from week 27 until birth (around week 40).