Pregnancy Due Date Calculator

Easily calculate your due date, track your pregnancy week-by-week milestones, and monitor your baby's growth with our free, accurate calculator.

This tool helps expectant mothers and healthcare professionals estimate key pregnancy dates, including the due date, current week, trimester, and upcoming milestones. Simply enter the first day of your last menstrual period to get started.

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Pregnancy Week-by-Week Milestones

Week Milestone Baby Size
Results are estimations based on averages for single pregnancies.

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How We Estimate Your Due Date

Our calculator uses the standard Naegele's rule: 40 weeks (280 days) from the first day of your last menstrual period (LMP). This method assumes a regular 28-day cycle with ovulation occurring on day 14. Only about 5% of women deliver on their exact due date, but most deliver within 2 weeks before or after.

Why Track Your Pregnancy Milestones?

Tracking your pregnancy week-by-week helps you understand your baby's development and anticipate changes in your body. It allows you to prepare for important prenatal tests, make informed decisions about your care, and bond with your growing baby by learning about their progress each week.

Frequently Asked Questions

The calculator is about 95% accurate for women with regular 28-day cycles. If your cycles are irregular or you ovulated at a different time than day 14, your actual due date may vary. An ultrasound in the first trimester can provide a more accurate estimate.

If you're unsure about your last period date, try to recall any significant events around that time that might help jog your memory. Alternatively, an early ultrasound can provide an accurate estimate. The earlier the ultrasound, the more accurate the dating.

Twins and multiples often arrive earlier than single babies. While the due date calculation method is the same, your healthcare provider will likely monitor you more closely as multiples have a higher chance of premature birth. The average twin pregnancy lasts about 36 weeks.

Trusted Sources

  • American College of Obstetricians and Gynecologists (ACOG)
  • Mayo Clinic Pregnancy Guidelines
  • World Health Organization (WHO)
  • National Institutes of Health (NIH)

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