Note: This calculator uses Naegele's Rule (LMP + 280 days, adjusted for cycle length) to estimate your due date. Results are for reference only. Natural delivery typically occurs between 37 and 42 weeks. Always consult your healthcare provider; ultrasound dating is the most accurate.
What is an Estimated Due Date?
The Estimated Due Date (EDD) is the predicted date when your baby will be born — typically calculated as 280 days (40 weeks) from the first day of your last menstrual period (LMP). This method, known as Naegele's Rule, is the most widely used due-date estimation worldwide.
How is the Due Date Calculated?
This tool calculates as follows:
Start from the first day of your last menstrual period;
For a standard 28-day cycle, add 280 days to get the due date;
For other cycle lengths, adjust by (cycle length − 28) days to account for ovulation timing;
Based on today's date, calculate the weeks and days you've been pregnant, plus time remaining until your due date.
What are the Pregnancy Trimesters?
First trimester (weeks 1–12): Critical period of organ formation. The NT (nuchal translucency) scan is performed at 11–13⁺⁶ weeks.
Second trimester (weeks 13–27): Rapid fetal development. Key screenings include Down syndrome screening and the anatomy ultrasound.
Third trimester (weeks 28–40): Fetal weight gain and delivery preparation. Gestational diabetes screening and weekly prenatal visits.