Pregnancy Due-Date Calculator
Estimate your due date, gestational age, and trimester milestones.
Current Gestational Age: 8 Weeks, 0 Days
About the Pregnancy Due-Date Calculator
The Pregnancy Due-Date Calculator estimates your expected delivery date (EDD) using established obstetrical principles (Naegele’s Rule) with adjustments for individual menstrual cycle lengths. It also provides your current gestational age in completed weeks and days, along with a trimester timeline.
How to Use This Calculator
- Choose calculation method: First Day of Last Menstrual Period (LMP) or Date of Conception.
- Enter the relevant date.
- Adjust your Average Menstrual Cycle Length (default 28 days, adjustable from 21 to 35 days).
- Click Calculate to inspect your estimated due date and trimester milestones.
Calculation Method & Mathematical Formula
Based on extended Naegele’s Rule:
EstimatedDueDate = LMP + 280 days + (CycleLength - 28 days)
From conception: EstimatedDueDate = ConceptionDate + 266 days.
Worked Example
Scenario: LMP on January 15, 2026 (28-day cycle):
- Estimated Due Date (EDD): October 22, 2026 (Thursday).
- First Trimester Ends: Week 13 (April 16, 2026).
- Second Trimester Ends: Week 27 (July 23, 2026).
- Third Trimester: Weeks 28 to 40+.
Important Calendar Notes
Only about 4% to 5% of babies are born precisely on their estimated due date; the vast majority arrive within a window of two weeks before or after.