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EDD Calculator & Pregnancy Tracker – Calculate Estimated Due Date

Accurately calculate your Estimated Due Date (EDD) and track your pregnancy week by week. Supports Naegele's rule (LMP with menstrual cycle adjustments), exact conception date, IVF embryo transfer (Day 3 & Day 5), and ultrasound gestational dating.

How to Use the EDD Calculator

  1. Select your calculation method: Last Menstrual Period (LMP), Conception Date, IVF Embryo Transfer, or Ultrasound Scan.
  2. Enter the date of your last period or conception.
  3. Adjust your average menstrual cycle length (default is 28 days; adjusts if your cycle is shorter or longer).
  4. Instantly view your calculated Estimated Due Date (EDD), exact gestational age (weeks and days), and remaining delivery countdown.
  5. Track your current trimester and view upcoming prenatal milestones, ultrasound scan windows, and screening tests.
  6. Export or print your complete EDD timeline and medical schedule as a PDF or Excel report.

Estimated Due Date Formulas & Rules Explained

Obstetricians and maternal healthcare providers calculate the Estimated Due Date (EDD) using established clinical rules: 1. Naegele's Rule (LMP with Cycle Adjustment): • Standard 28-day cycle: EDD = LMP + 280 Days (40 Weeks / 10 Lunar Months) • Cycle Length Adjustment: EDD = LMP + 280 Days + (Cycle Length - 28 Days) • Quick Calculation: (LMP Date + 1 Year) - 3 Months + 7 Days (for a standard 28-day cycle). 2. Conception Date Method (Ovulation): • EDD = Conception Date + 266 Days (38 Weeks / 266 Gestational Days from fertilization). 3. IVF Embryo Transfer Method: • Day 5 Blastocyst Transfer: EDD = Transfer Date + 261 Days • Day 3 Embryo Transfer: EDD = Transfer Date + 263 Days 4. Ultrasound Dating (Crown-Rump Length): • EDD = Ultrasound Date + (280 - Gestational Age in Days at Scan). First-trimester crown-rump length (CRL) is considered the most accurate baseline if LMP is uncertain. 5. Gestational Trimesters: • 1st Trimester: Conception to 13 Weeks 6 Days (Organogenesis) • 2nd Trimester: 14 Weeks to 27 Weeks 6 Days (Rapid Growth) • 3rd Trimester: 28 Weeks to Delivery (Maturation & Weight Gain)

Example 1: Regular 28-Day Cycle via LMP

LMP: 1 February 2026 | Cycle Length: 28 Days

EDD = Feb 1, 2026 + 280 Days Estimated Conception = Feb 15, 2026 (Day 14) Full-term milestone = Oct 18, 2026 (Week 37)

Estimated Due Date (EDD): November 8, 2026 (40 Weeks 0 Days)

Example 2: Longer 32-Day Menstrual Cycle

LMP: 10 January 2026 | Cycle Length: 32 Days (+4 days adjustment)

Standard EDD = Oct 17, 2026 Adjusted EDD (+4 days for delayed ovulation) = Oct 21, 2026 Estimated Ovulation = Day 18

Estimated Due Date (EDD): October 21, 2026

Example 3: IVF Day-5 Blastocyst Embryo Transfer

Method: IVF Day 5 | Transfer Date: 15 March 2026

EDD = March 15, 2026 + 261 Days Equivalent LMP Date = March 1, 2026

Estimated Due Date (EDD): December 1, 2026

Clinical Best Practices & Advice

  • ✓Only 4% to 5% of babies arrive on their exact calculated EDD. A normal full-term birth window spans anywhere between 37 weeks and 42 weeks.
  • ✓If your first-trimester dating ultrasound scan differs from your LMP date by more than 7 days, obstetricians generally adopt the ultrasound EDD.
  • ✓Track your gestational weeks carefully to schedule critical prenatal tests on time: NT scan (weeks 11-13), Anomaly scan (weeks 18-20), and Gestational Diabetes screen (weeks 24-28).
  • ✓If you have irregular periods or PCOS, calculate your EDD using an early dating ultrasound scan rather than LMP.

Common Misconceptions to Avoid

  • ✗Assuming pregnancy is strictly 9 calendar months. Medically, gestational age is measured as 40 completed weeks (280 days) from the first day of your last period.
  • ✗Forgetting to adjust for menstrual cycle lengths longer or shorter than 28 days when using Naegele's rule.
  • ✗Confusing the conception date with the LMP date (LMP is approximately 2 weeks earlier than conception).
  • ✗Panicking if delivery does not occur exactly on the calculated EDD; normal labor usually occurs within two weeks before or after.

Frequently Asked Questions (FAQs)

EDD stands for Estimated Due Date (or Estimated Date of Delivery). It is the predicted date on which spontaneous labor is expected. It is calculated by adding 280 days (40 weeks) to the first day of your last menstrual period (LMP) according to Naegele's rule.
While only about 4-5% of babies are born on the exact day of their EDD, roughly 80% to 90% of healthy infants are born within a two-week window (between 37 and 42 weeks of gestation). It serves as a vital clinical benchmark to monitor fetal development and plan medical checkups.
If you have irregular menstrual cycles or PCOS, LMP calculations may be inaccurate. In such cases, an early first-trimester ultrasound scan (performed between 7 and 13 weeks measuring Crown-Rump Length) provides the most reliable Estimated Due Date.
Yes. If an early dating ultrasound scan (before 14 weeks) shows a discrepancy of more than 5 to 7 days compared to the LMP-calculated date, your healthcare provider may formally update your official EDD to match the ultrasound measurements.
For IVF pregnancies, the exact embryo transfer date and embryonic age are precisely known. For a Day 5 blastocyst transfer, the EDD is calculated as Transfer Date + 261 days. For a Day 3 embryo transfer, it is Transfer Date + 263 days.
Gestational age is measured from the first day of your last menstrual period (LMP) and is typically 40 weeks. Fetal age (conceptional age) is measured from the actual time of fertilization and is approximately two weeks shorter (38 weeks).
Pregnancy is divided into three trimesters: First Trimester (Week 1 through Week 13), Second Trimester (Week 14 through Week 27), and Third Trimester (Week 28 through Delivery). A baby reaches full term at 37 completed weeks.
Key prenatal scans include the Early Dating / Viability Scan (weeks 6-9), Nuchal Translucency / NT Scan (weeks 11-13), Fetal Anomaly / Level II Scan (weeks 18-20), and Growth / Doppler Scans during the third trimester (weeks 28-36).

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Last updated: 2026-10-06