Calculate your estimated due date (EDD) using Naegele's Rule, conception date, or IVF transfer date. This pregnancy due date calculator gives your gestational age in weeks and days, trimester, days remaining, baby size comparison, and key appointment dates. Fast, private, no signup.
Quick answer: EDD = LMP + 280 days (Naegele's Rule). Adjust for cycle length. See How Due Date Is Calculated, Due Date Accuracy and Trimester Guide — or jump to BMI Calculator and TDEE Calculator.
Estimate your baby's arrival date
The most widely used method for estimating a due date is Naegele's Rule, named after the 19th-century German obstetrician Franz Naegele. It is simple, well-established, and used by healthcare providers worldwide.
Naegele's Rule (Standard)
EDD = LMP + 280 days
Add 40 weeks (280 days) to the first day of your last menstrual period
Cycle-Adjusted
EDD = LMP + 280 + (cycle − 28)
Adjusts for cycles shorter or longer than the 28-day average
Conception Date
EDD = Conception + 266 days
From the known date of conception (fertilization)
IVF Transfer
EDD = Transfer + 266 (5-day) or + 280 (3-day)
Based on embryo age at transfer — 3-day or 5-day blastocyst
Despite its simplicity, Naegele's Rule assumes a 28-day menstrual cycle with ovulation on day 14. Our calculator adjusts for actual cycle length and supports all three methods for a more personalized estimate.
A due date is an estimate, not a guarantee. Research consistently shows that only about 5% of babies are born on their exact due date, while roughly 90% are born within ±5 days of the estimate.
Factors that can affect due date accuracy include irregular cycles, uncertain LMP, late ovulation, and individual variation in implantation timing. First-trimester ultrasound is the gold standard for dating when available.
It is completely normal for a due date to be adjusted after an ultrasound. In fact, about 40% of pregnancies have their due date changed after first-trimester dating. Here is why:
If your provider changes your due date, trust the new estimate. Early ultrasound dating is more reliable than LMP-based calculations because babies develop at a more consistent rate in early pregnancy than the timing of ovulation varies.
Pregnancy is divided into three trimesters, each with distinct developmental milestones and prenatal care needs.
Understanding when key appointments happen helps you prepare. This calculator estimates dates based on your due date.
| Appointment | When | Purpose |
|---|---|---|
| Dating Scan | ~8 weeks | Confirm pregnancy, check heartbeat, verify due date |
| Anatomy Scan | ~20 weeks | Detailed check of baby's organs, growth, and development |
| Glucose Tolerance Test | ~28 weeks | Screen for gestational diabetes |
| Group B Strep Test | ~36 weeks | Screen for GBS infection that could affect baby during delivery |
| Due Date | ~40 weeks | Estimated due date — monitor closely for signs of labor |
This pregnancy due date calculator provides an estimate based on standard medical formulas and is for educational and informational purposes only.
Results should not be used as a substitute for professional medical advice, diagnosis, or treatment. Always consult your healthcare provider for personalized pregnancy dating and prenatal care.
Due date estimates are approximations. Actual delivery timing depends on many factors including ovulation timing, implantation, and individual variation. Only about 5% of babies are born on their exact estimated due date.
The most common method is Naegele's Rule: add 280 days (40 weeks) to the first day of your last menstrual period (LMP). This calculator also supports cycle-length adjustment, conception date (add 266 days), and IVF transfer date methods for more personalized estimates.
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This pregnancy due date calculator is for informational purposes only and does not replace medical advice. Always consult a healthcare professional for prenatal care.
Content Updated At: 01/09/2026 · Reviewed · ACOG/WHO aligned
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