Pregnancy Tools
When Will Your Baby Arrive?
Enter your last menstrual period to calculate your estimated due date, conception window, and complete pregnancy timeline.
Estimated Due Date
Your Pregnancy Timeline
How Is My Due Date Calculated?
Your estimated due date is calculated using Naegele's rule — the standard method used by obstetricians worldwide. It adds 280 days (40 weeks) to the first day of your last menstrual period.
Only about 4% of babies are born exactly on their due date. Most arrive within a window of two weeks before or after. Think of your due date as a helpful estimate — not a deadline.
What If I Don't Know My LMP Date?
If you're unsure about your last period date, your healthcare provider can estimate your due date using an early ultrasound, which measures the size of the developing embryo. First-trimester ultrasounds are the most accurate for dating a pregnancy.
What If My Cycles Are Irregular?
Naegele's rule assumes a 28-day cycle with ovulation on day 14. If your cycles are longer or shorter, your actual due date may differ. Mention irregular cycles to your provider so they can adjust accordingly.
The Three Trimesters
First Trimester (Weeks 1–13)
The most critical period of development. Baby's major organs, spinal cord, and brain begin forming. You may experience fatigue, nausea, and breast tenderness. This is when most miscarriages occur, so rest and prenatal care are essential.
Second Trimester (Weeks 14–27)
Often called the "golden trimester." Energy returns, nausea typically subsides. You'll feel baby's first movements around weeks 18–22. The anatomy scan around week 20 checks baby's development in detail.
Third Trimester (Weeks 28–40)
Baby is growing rapidly, gaining weight, and preparing for birth. You may feel Braxton Hicks contractions. After 37 weeks, baby is considered full-term. Pack your hospital bag by week 35.
Frequently Asked Questions
How accurate is this calculator?
This calculator follows the same Naegele's rule that most OB-GYNs use. It's about 95% accurate within a ±2-week window. For a more precise estimate, ask your provider about a dating ultrasound.
Can I calculate from conception date instead?
Yes! Select "Conception Date" above. We'll add 266 days to estimate your due date. This method can be slightly more accurate if you know exactly when you ovulated.
What if I conceived via IVF?
Choose the "IVF Transfer" option above. For a 3-day embryo transfer, we calculate 263 days from the transfer date. For a 5-day blastocyst transfer, we use 261 days.
Why 40 weeks when pregnancy is 9 months?
Pregnancy is measured from the first day of your last period — about two weeks before conception actually occurs. So the developmental pregnancy is about 38 weeks, but the clinical measurement is 40 weeks.