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Due Date Tracker

Pregnancy Due Date Calculator (Naegele's Rule)

Estimate your due date and current week of pregnancy from your last period, conception date, or an ultrasound.

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Pregnancy Due Date Calculator
Estimate your due date and track key pregnancy milestones by trimester
Enter your dates to calculate due date

Medical disclaimer. This calculator is provided for educational and informational purposes only and does not constitute medical advice, diagnosis, or treatment. Always consult a qualified healthcare professional regarding your health, diet, exercise, or medication decisions. Read full disclaimer →

About Pregnancy Due Date Calculator

The estimated due date (EDD) is calculated by Naegele rule: add 40 weeks (280 days) to the first day of your last menstrual period (LMP). This assumes a regular 28-day cycle with ovulation on day 14. For cycles other than 28 days, adjust the EDD by the difference from 28 days. Gestational age is counted from the LMP, not from conception - which is approximately 2 weeks after LMP.

Pregnancy trimesters: First trimester weeks 1-12 (critical organ development); Second trimester weeks 13-26 (growth period, typically most comfortable); Third trimester weeks 27-40 (rapid growth, preparation for birth). Only approximately 5% of babies are born on their exact EDD - normal delivery is 37-42 weeks. An ultrasound at 8-12 weeks provides the most accurate dating when cycle length is irregular. Always confirm dates with your gynaecologist.

Frequently Asked Questions

The default method uses Naegele's rule: add 280 days (40 weeks) to the first day of your last menstrual period (LMP). This assumes a regular 28-day cycle with ovulation occurring on day 14. You can also calculate from an estimated conception date, or from an ultrasound dating (weeks pregnant at the time of the scan).
Gestational age is conventionally counted from the first day of the LMP, which is typically about two weeks before conception actually occurs. This convention exists because the LMP date is usually more reliably known than the exact conception date, even though actual fetal development begins roughly two weeks later.
Only about 5% of babies are born on their exact estimated due date. Normal, full-term delivery falls anywhere in the 37-42 week range. An early ultrasound (typically at 8-12 weeks) tends to provide the most accurate dating, especially useful when your cycle length is irregular and Naegele's rule (which assumes a 28-day cycle) is less reliable.
The first trimester (weeks 1-12) is the critical period for organ development. The second trimester (weeks 13-26) is typically the most comfortable, with steady fetal growth. The third trimester (weeks 27-40) involves rapid growth and the body's preparation for birth. This calculator shows which trimester you're currently in based on your estimated dates.
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