Due Date Calculator

Calculate your estimated delivery date (EDD), current gestational age, trimester timeline, and important prenatal screening milestones.

Calculate Estimated Due Date

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Key Takeaway: A clinical due date represents 40 weeks from your last period. Healthy full-term delivery typically occurs anytime between 37 and 42 weeks.

Naegele's Rule with Cycle Adjustment

Standard Naegele's rule assumes a 28-day cycle with ovulation occurring precisely on Day 14 (280 days from LMP). Our engine adjusts for longer or shorter follicular phases:

Adjusted EDD = LMP + 280 + (Cycle Length − 28) days

When to See a Doctor

Online calculators provide general estimates based on biological averages. Consult a healthcare provider (such as an OB/GYN or general practitioner) if you notice:

  • Your periods suddenly become irregular after being consistent
  • Your cycle is consistently shorter than 21 days or longer than 35 days
  • Your period bleeding lasts longer than 7 days or is unusually heavy (soaking through a pad/tampon every hour)
  • You experience severe, debilitating pelvic pain or cramping that disrupts daily life
  • You experience bleeding between periods or after intercourse
  • You are under 35 and have been trying to conceive for 12 months (or 6 months if 35+)
  • Your period has stopped completely for 90 days or more (and you are not pregnant)
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Check Pregnancy Week & Day

Track detailed weekly developmental milestones throughout your pregnancy.

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Frequently Asked Questions

Evidence-based answers to common questions about your cycle and fertility.

How is a pregnancy due date calculated?

A clinical due date is calculated using Naegele's rule by adding 280 days (40 weeks) to the first day of your last menstrual period (LMP). If your cycle differs from 28 days, the calculation adjusts by adding (Cycle Length − 28) days.

What percentage of babies are born on their exact due date?

Only about 4% to 5% of babies are born on their exact estimated due date. Most spontaneous births occur within a normal term window between 37 weeks 0 days and 41 weeks 6 days.

Is an ultrasound due date more accurate than LMP?

Yes. A first-trimester crown-rump length (CRL) ultrasound scan performed between 8 and 13 weeks is the clinical gold standard for establishing gestational age and can override LMP dates if the discrepancy exceeds 5 to 7 days.

Explore other free, private tools for tracking your menstrual cycle and fertility.

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Medical & Scientific Sources

  1. American College of Obstetricians and Gynecologists (ACOG)(2017). "Method for Estimating the Due Date (Committee Opinion No. 700)"
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