📅 Due Date Calculator
Calculate your estimated due date (EDD) based on your last menstrual period (LMP) using Naegele's rule.
Most women have 28-day cycles, but this can vary (21-35 days)
Understanding Due Date Calculation
Your due date is calculated by adding 280 days (40 weeks) to the first day of your last menstrual period (LMP). This is known as Naegele's rule, named after the German obstetrician Franz Naegele who devised this method in the 19th century.
How It Works
Naegele's Rule:
Due Date = LMP + 280 days (or 9 months + 7 days)
Pregnancy Trimesters
| Trimester | Weeks | Key Developments |
|---|---|---|
| First | 1-12 | Major organs form, heartbeat begins |
| Second | 13-27 | Movement felt, gender visible, rapid growth |
| Third | 28-40 | Final development, weight gain, preparation for birth |
Important: Only about 5% of babies are born on their exact due date. Most babies arrive between 37 and 42 weeks. This calculator provides an estimate - your healthcare provider will monitor your pregnancy and may adjust dates based on ultrasound measurements.