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Pregnancy Due Date Calculator

Excited about your new baby? Calculate your estimated due date and see which trimester you are in right now.

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Enter your dates to see when your baby arrives

How to Use This Pregnancy Calculator

Calculating your due date helps you prepare for your baby's arrival and track your pregnancy milestones:

  1. Enter the first day of your last period – This is the date most commonly used for calculations.
  2. Or enter your conception date – If you know when you conceived, this provides a more precise estimate.
  3. View your due date – See your estimated delivery date (EDD).
  4. Track your progress – See how many weeks pregnant you are and which trimester you're in.

Remember, only about 5% of babies are born on their exact due date. Most healthy pregnancies deliver between 38-42 weeks.

How Is the Due Date Calculated?

Healthcare providers use a standard method called Naegele's Rule to calculate your estimated due date:

  • Add 280 days (40 weeks) to the first day of your last menstrual period (LMP)
  • Or add 266 days (38 weeks) from your conception date

This method assumes a 28-day cycle with ovulation occurring on day 14. If your cycles are longer or shorter, your due date may be adjusted. Ultrasound dating, especially in the first trimester, can provide a more accurate estimate and may override the LMP calculation if there's a significant difference.

Formula: LMP + 7 days - 3 months + 1 year = Due Date

Understanding the Three Trimesters

Pregnancy is divided into three trimesters, each with unique developments and milestones:

First Trimester (Weeks 1-12)

  • Baby develops major organs, brain, and spinal cord
  • Heartbeat can be detected around week 6
  • Common symptoms: morning sickness, fatigue, breast tenderness
  • Important time for prenatal vitamins, especially folic acid

Second Trimester (Weeks 13-26)

  • Often called the "honeymoon phase" as morning sickness typically subsides
  • You'll start feeling baby's movements (quickening) around weeks 16-22
  • Baby's sex can be determined via ultrasound around week 18-20
  • Baby develops hearing and can recognize your voice

Third Trimester (Weeks 27-40)

  • Baby gains weight rapidly and organs mature
  • You may experience Braxton Hicks contractions
  • Baby typically moves into head-down position for birth
  • Nesting instinct may kick in as you prepare for arrival

Important Pregnancy Milestones

Here are key milestones to look forward to during your pregnancy journey:

  • Week 4: Positive pregnancy test possible
  • Week 6-7: First heartbeat visible on ultrasound
  • Week 8-10: First prenatal appointment typically scheduled
  • Week 10-13: First trimester screening tests available
  • Week 12: Risk of miscarriage drops significantly
  • Week 16-20: Feel first movements (earlier for second+ pregnancies)
  • Week 18-22: Anatomy scan ultrasound
  • Week 24: Viability milestone - baby has chance of survival if born early
  • Week 28: Third trimester begins; more frequent prenatal visits
  • Week 37: Pregnancy considered "early term"
  • Week 39-40: Full term; optimal time for delivery

Frequently Asked Questions

How accurate is the due date calculation?

Due dates are estimates. Only about 5% of babies are born on their exact due date. About 80% of babies are born within two weeks of their due date (between 38-42 weeks). First-trimester ultrasounds can provide accuracy within 5-7 days.

What if I don't know my last period date?

If you're unsure of your last period, your healthcare provider can estimate your due date using an early ultrasound. First-trimester ultrasounds (before 13 weeks) are most accurate for dating, measuring the baby's crown-to-rump length.

Can my due date change?

Yes, your due date may be adjusted if early ultrasound measurements differ significantly from your LMP calculation (usually by more than 7 days). Later ultrasounds are less accurate for dating because babies grow at different rates.

What does "weeks pregnant" mean exactly?

Pregnancy is counted from the first day of your last period, not from conception. So at "4 weeks pregnant," you actually conceived about 2 weeks ago. This is why pregnancy lasts "40 weeks" even though the baby develops for about 38 weeks.

When should I tell people I'm pregnant?

Many people wait until after the first trimester (12 weeks) when the risk of miscarriage drops significantly. However, this is a personal decision. Some prefer to share earlier for support, while others wait for genetic testing results around weeks 10-13.

Tips for a Healthy Pregnancy

Taking care of yourself during pregnancy helps ensure the best outcomes for you and your baby:

  • Take prenatal vitamins: Folic acid is especially important for preventing neural tube defects
  • Attend all prenatal appointments: Regular check-ups monitor your health and baby's development
  • Eat a balanced diet: Focus on proteins, whole grains, fruits, vegetables, and healthy fats
  • Stay hydrated: Aim for 8-10 glasses of water daily
  • Exercise moderately: Walking, swimming, and prenatal yoga are generally safe
  • Get enough sleep: Rest becomes more important as your body works harder
  • Avoid harmful substances: No alcohol, smoking, or recreational drugs; limit caffeine
  • Manage stress: Practice relaxation techniques and seek support when needed

Disclaimer: This calculator provides estimates for informational purposes only. Always consult with your healthcare provider for medical advice and to confirm your due date.