Pregnancy Due Date Calculator
Calculate your estimated due date (EDD) based on last menstrual period, conception date, or ultrasound. Get a week-by-week pregnancy timeline.
🤰 Life Events📐 EDD = Last Menstrual Period + 280 days (Naegele's Rule)
Year of last period (YYYY)
Month (1-12)
Day of last period
Average cycle length (days)
Calculation method
Please enter valid values.
Formula & Reference
| Variable | Formula | Units |
|---|---|---|
| Pregnancy Due Date Calculator | EDD = Last Menstrual Period + 280 days (Naegele's Rule) | estimated date |
Step-by-Step Examples
Example 1
June 15 LMP
LMP June 15, 2025, 28-day cycle.
- EDD = June 15 + 280 days = March 21, 2026
- Week 1 of pregnancy starts at LMP
✓ Estimated due date: March 21, 2026
Example 2
Short Cycle
LMP June 1, 25-day cycle.
- Cycle adjust: 25-28 = -3 days
- EDD = June 1 + 277 days = March 4, 2026
✓ March 4, 2026 (3 days earlier)
Example 3
Long Cycle
LMP June 1, 35-day cycle.
- EDD = June 1 + 287 days = March 14, 2026
- Adjusted for 35-day cycle (+7 days)
✓ March 14, 2026
Real-World Applications
Pregnant People
Calculate your due date and track your pregnancy timeline.
OBGYNs
Quick due date reference tool.
Family Planners
Plan for important pregnancy milestones.
New Parents
Calculate key dates for work leave, preparation, and nursery.
Common Mistakes to Avoid
⚠️
Due dates are estimates
Only 4-5% of babies are born on their exact due date. Full-term is 37-42 weeks; most births occur within 2 weeks of the due date.
⚠️
First trimester ultrasound is most accurate
If there's a discrepancy between LMP-based and ultrasound-based dates, the first-trimester ultrasound (7-12 weeks) is more accurate and typically becomes the official due date.
⚠️
Irregular cycles affect accuracy
LMP-based dates assume a 28-day cycle with ovulation on day 14. Irregular cycles, PCOS, or recent hormonal contraceptive use reduces accuracy. Ultrasound confirmation is especially important with irregular cycles.
Frequently Asked Questions
What is Naegele's Rule? ▾
The standard due date formula: EDD = LMP + 280 days (9 months, 7 days). Developed in the 1800s and still widely used. Assumes 28-day cycles with ovulation on day 14.
What are the trimesters? ▾
First trimester: weeks 1-13. Second trimester: weeks 14-27. Third trimester: weeks 28-40+. Each trimester brings different developmental milestones and physical changes.
What if I don't know my last period? ▾
Early ultrasound (6-10 weeks) measures the embryo to determine gestational age and calculate EDD. This is often more accurate than LMP-based calculation, especially with irregular cycles.
What is full term? ▾
37-40 weeks is full term. 37-38 weeks is early term. 39-40 weeks is full term (optimal). 41 weeks is late term. 42+ weeks is post-term (providers discuss induction). Preterm is before 37 weeks.
What prenatal care schedule is typical? ▾
Weeks 4-28: monthly visits. Weeks 28-36: every 2 weeks. Weeks 36-40+: weekly. Total: approximately 10-14 prenatal visits. First visit is usually at 8-10 weeks to confirm pregnancy and dating ultrasound.