Due Date Calculator (Pregnancy Estimator)
Estimate your baby's due date with our free Due Date Calculator. Simply enter the first day of your last menstrual period and your average cycle length to get your estimated due date, current pregnancy week, trimester breakdown, and weekly milestones. This tool uses the standard Naegele's rule for accurate pregnancy dating.
Due Date Calculator
Your Due Date Results
Pregnancy Timeline
| Week | Dates | Trimester | Milestone |
|---|
How to Use the Tool
1. Enter LMP
First day of your last period.
2. Set cycle length
Your average cycle length.
3. Get insights
Due date, week, trimester & timeline.
How It's Calculated
Key Formulas
- Ovulation Day: Cycle Length − 14
- Conception: LMP + Ovulation Day
- Due Date: Conception + 266 days
- Alternative: LMP + 280 days (Naegele's Rule)
Trimesters
- First Trimester: Weeks 1–13
- Second Trimester: Weeks 14–27
- Third Trimester: Weeks 28–40+
About Due Dates
What is a Due Date?
A due date is an estimate of when your baby is likely to be born. It is calculated based on the first day of your last menstrual period (LMP) and your average cycle length. The average pregnancy lasts about 280 days (40 weeks) from the first day of your LMP. Only about 5% of babies are born on their exact due date — most arrive between 37 and 42 weeks.
Key Facts:
- Naegele's Rule: LMP + 280 days = Due Date
- Full Term: 39 weeks to 40 weeks + 6 days
- Early Term: 37 weeks to 38 weeks + 6 days
- Post-Term: 42 weeks and beyond
Limitations of This Tool
- Assumes a regular 28-day cycle — irregular cycles may affect accuracy.
- Does not account for conception date variations or ovulation timing.
- Not a substitute for professional medical advice or ultrasound dating.
- Due dates are estimates — only about 5% of babies arrive on their due date.
Trust & Privacy
Your data stays in your browser. All calculations happen locally. We never send your data to any server.
No registration or login required. Your privacy is 100% protected.
Uses Naegele's rule & standard methods. Our tool follows established pregnancy dating principles.
No cookies used for tracking. Your history is stored locally in your browser's localStorage.
Real-World Examples
LMP: Jan 1, Cycle: 28 days
Due Date: Oct 7
LMP: Mar 15, Cycle: 30 days
Due Date: Dec 19
LMP: Jun 1, Cycle: 26 days
Due Date: Mar 7
Frequently Asked Questions
References
- American College of Obstetricians and Gynecologists. Methods for Estimating the Due Date. acog.org
- World Health Organization. Pregnancy, childbirth, postpartum and newborn care. who.int
- National Institutes of Health. Pregnancy and Childbirth. nichd.nih.gov