Pregnancy Due Date Calculator
Calculate your baby's due date based on your last menstrual period or conception date
Understanding Pregnancy Due Dates
A pregnancy due date calculator helps estimate when your baby will arrive. Most pregnancies last about 40 weeks (280 days) from the first day of your last menstrual period, though only about 5% of babies are born exactly on their due date.
Calculation Methods
Last Menstrual Period (LMP)
The most common method adds 280 days (40 weeks) to the first day of your last menstrual period. This method assumes ovulation occurred on day 14 of a 28-day cycle.
Conception Date
If you know the exact conception date, this method adds 266 days (38 weeks) to that date. This is more accurate if you're certain of when conception occurred.
How to Use This Calculator
- Choose your calculation method (LMP or Conception Date)
- Enter the first day of your last menstrual period or conception date
- Optionally adjust your average cycle length if it differs from 28 days
- Click "Calculate Due Date" to see your results
Important Considerations
- Due dates are estimates - babies are considered full-term between 37-42 weeks
- Only 5% of babies are born exactly on their due date
- First-time mothers often deliver after their due date
- Ultrasound dating in early pregnancy can be more accurate than LMP dating
- Always consult your healthcare provider for medical advice
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Frequently Asked Questions
How accurate are pregnancy due date calculators?
Due date calculators provide estimates based on average pregnancy lengths. They're most accurate when based on a known last menstrual period or conception date, but only about 5% of babies are born exactly on their due date.
What if I don't remember my last menstrual period?
If you can't remember your LMP, try using the conception date method if you know when conception occurred. Otherwise, an early pregnancy ultrasound can provide the most accurate dating.
Can my due date change during pregnancy?
Your healthcare provider may adjust your due date based on ultrasound measurements, especially if done in the first trimester. Early ultrasounds are generally more accurate than LMP dating.
When is it safe for my baby to be born?
Babies are considered full-term between 37-42 weeks of pregnancy. Babies born before 37 weeks are premature, while those born after 42 weeks are post-term. Both situations may require special medical attention.