Pregnancy Due Date Calculator
Estimate your expected delivery date using multiple methods: last menstrual period (Naegele's rule), conception date, IVF transfer date, or ultrasound measurements for the most accurate prediction.
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⚠️For informational purposes only — not medical advice. Consult a healthcare professional before acting on results.
Estimate your expected delivery date using multiple methods: last menstrual period (Naegele's rule), conception date, IVF transfer date, or ultrasound measurements. First-trimester ultrasound provides the most accurate prediction (±7 days). Full term is 39-40 weeks.
Sources: ACOG, WHO, NIH, CDC.
Key Takeaways
- • LMP + 280 days (+ cycle adjustment) = standard EDD
- • Ultrasound before 14 weeks is most accurate for dating
- • IVF: Day 5 transfer + 261 days, Day 3 + 263 days
- • Only ~5% of babies arrive on their exact due date
Did You Know?
How Does Pregnancy Due Date Work?
LMP Method
Add 280 days to first day of last period. Adjust for cycle length if not 28 days.
Conception Method
Add 266 days to known conception. Pregnancy from fertilization is ~38 weeks.
IVF & Ultrasound
IVF uses transfer date + embryo-specific days. Ultrasound uses GA at scan to back-calculate EDD.
Expert Tips
Method Comparison
| Method | Accuracy | Best For |
|---|---|---|
| LMP | ±1-2 wks | Regular cycles |
| Conception | ±3-5 days | Tracked ovulation |
| Ultrasound | ±5-7 days | First trimester |
| IVF | Exact | Assisted reproduction |
Frequently Asked Questions
What methods can I use to calculate my due date?
You can use four methods: Last Menstrual Period (Naegele's rule), known conception date, IVF transfer date, or first-trimester ultrasound. Ultrasound dating is most accurate (±5-7 days) when done before 14 weeks.
How accurate is each due date method?
IVF and conception date methods are most accurate (known dates). First-trimester ultrasound is ±5-7 days. LMP with regular cycles is ±1-2 weeks. LMP with irregular cycles has ±2-3 week variance.
What is full term vs early term?
Full term is 39-40 weeks—the optimal delivery window. Early term is 37-38 weeks when the baby is considered term but not yet optimal. Late term is 41 weeks; post-term is 42+ weeks.
When should I get a dating ultrasound?
The best window is 6-10 weeks for viability and dating. First-trimester screening (11-14 weeks) can also establish dates. After 24 weeks, ultrasound is not used to change due dates.
Does cycle length affect my due date?
Yes. For cycles longer than 28 days, add (cycle length - 28) days to your EDD. For shorter cycles, subtract. Example: 35-day cycle adds 7 days to the standard LMP calculation.
Can I use this calculator for IVF pregnancies?
Yes. Enter your embryo transfer date and embryo age (Day 3, 5, or 6). Day 5 blastocyst adds 261 days; Day 3 adds 263 days. IVF provides the most precise due date calculation.
Key Statistics
Official Data Sources
⚠️ Disclaimer: This calculator is for educational and informational purposes only. It is not a substitute for professional medical advice, diagnosis, or treatment. Always consult a qualified healthcare provider for pregnancy dating and prenatal care.