Health & Fitness
Pregnancy Due Date Calculator
Estimate your due date, conception date, current pregnancy week, and trimester using Naegele's rule based on your last menstrual period.
Enter your details and click Calculate
Estimated Due Date
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How is this calculated?
Formula: Naegele's rule with cycle length adjustment.
Naegele's Rule (adjusted):
Due Date = LMP + 280 days + (Cycle Length − 28)
Conception Estimate:
Conception ≈ LMP + Cycle Length − 14
Current Week:
Week = floor((Today − LMP) / 7)
Trimester:
Weeks 1–13 → 1st Trimester
Weeks 14–27 → 2nd Trimester
Weeks 28–40 → 3rd Trimester
Days Remaining:
Remaining = Due Date − TodayCalculation history
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Medical Disclaimer: This calculator provides estimates for informational purposes only. It is not a substitute for professional medical advice, diagnosis, or treatment. Always consult your healthcare provider for accurate pregnancy dating and prenatal care.
FAQ
Frequently asked questions
How accurate is the due date calculation?
Due dates calculated using Naegele's rule are estimates — only about 5% of babies are born on their exact due date. Most births occur within 2 weeks before or after the estimated date. Ultrasound dating in the first trimester (before 13 weeks) is generally more accurate than LMP-based calculations.
What is Naegele's rule?
Naegele's rule estimates the due date by adding 280 days (40 weeks) to the first day of the last menstrual period (LMP). It assumes a 28-day cycle with ovulation on day 14. For cycles longer or shorter than 28 days, the formula adjusts by adding or subtracting the difference.
What if my cycle is irregular?
If your cycle is irregular, LMP-based calculations are less reliable. An early ultrasound (6–12 weeks) provides a more accurate due date. You can still use this calculator with your average cycle length, but discuss dating with your healthcare provider for the most accurate estimate.
How are trimesters divided?
The first trimester spans weeks 1–13 (conception through early development), the second trimester covers weeks 14–27 (rapid growth, movement felt), and the third trimester runs from week 28 until birth (around week 40). Each trimester has distinct developmental milestones and prenatal care needs.
When does conception actually occur?
Conception typically occurs around ovulation, which is approximately 14 days before the next period is due. For a 28-day cycle, this is around day 14. Sperm can survive up to 5 days, so conception can occur from intercourse several days before ovulation.