Due Date from LMP December 1, 2025
Calculate estimated due date from last menstrual period.
Calculate estimated due date from last menstrual period. Enter your First Day of Last Period to get an instant estimated due date. Formula: date_add(last_period, 280, "days").
Estimated Due Date
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How It Works
How It Works
The Pregnancy Due Date Calculator estimates your baby’s expected arrival date based on the first day of your last menstrual period. It uses a standard pregnancy length of 280 days, which equals 40 weeks.
Once you enter the first day of your last period, the calculator simply adds 280 days to that date. This method is commonly used by healthcare providers to give a general due date estimate.
- Enter the first day of your last menstrual period
- The calculator adds 280 days (40 weeks)
- This is the average length of a full-term pregnancy
- The result is your estimated due date
Understanding the Results
The date shown is an estimated due date, not an exact prediction of when your baby will be born. Most babies arrive within a couple of weeks before or after this date.
Your actual delivery date can vary depending on your cycle length, ovulation timing, and individual pregnancy factors. Your healthcare provider may adjust the date based on ultrasound results or other medical information.
- It is an estimate, not a guaranteed birth date
- Full-term pregnancy ranges from 37 to 42 weeks
- Only a small percentage of babies are born on the exact due date
- Your doctor may adjust the date after early ultrasounds
Frequently Asked Questions
How does the Pregnancy Due Date Calculator work?
This calculator estimates your due date by adding 280 days (40 weeks) to the first day of your last menstrual period. This method is based on the average length of a full-term pregnancy. It provides an estimated due date, which may be adjusted by your healthcare provider based on ultrasound results or other factors.
Why do I need to enter the first day of my last period?
Pregnancy is typically measured from the first day of your last menstrual period, not the date of conception. This is because ovulation and conception dates can vary and are often harder to pinpoint. Using your last period provides a standardized way to estimate gestational age and due date.
Is the calculated due date always accurate?
The calculated due date is an estimate, not a guarantee. Only about 5% of babies are born on their exact due date. Many factors, including cycle length and individual differences, can influence when labor begins.
What if I have irregular periods?
If your menstrual cycles are irregular, the estimated due date may be less accurate. In these cases, your healthcare provider may use an early ultrasound to determine a more precise due date. Always consult your provider for personalized guidance.
Can this calculator tell me how far along I am?
Yes, once your due date is estimated, you can count backward to determine your current week of pregnancy. Many pregnancy tracking tools use the same 40-week timeline starting from your last period. For the most accurate assessment, confirm your gestational age with your healthcare provider.
When should I see a doctor after calculating my due date?
You should schedule a prenatal appointment as soon as you suspect or confirm pregnancy. Early prenatal care is important for monitoring your health and your baby’s development. Your provider can confirm your due date and recommend the next steps in your pregnancy care.
Disclaimer
This calculator provides estimates for informational purposes only. It is not professional advice. Verify results with a qualified professional. Disclaimer.