When Baby Will Be Born Calculator
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Reviewed by Calculator Editorial Team
Pregnancy is a journey that begins with the first day of your last menstrual period (LMP). Our When Baby Will Be Born Calculator helps you track your pregnancy timeline by calculating your estimated due date based on your LMP or ultrasound date.
How to Use This Calculator
Using our calculator is simple:
- Enter the date of your first day of your last menstrual period (LMP)
- Alternatively, enter the date of your ultrasound if you have one
- Click "Calculate" to see your estimated due date
- Review the pregnancy timeline chart
The calculator uses standard pregnancy duration of 40 weeks (280 days) from the first day of your last menstrual period.
How the Calculation Works
The calculator uses the following formula to determine your estimated due date:
Formula
Estimated Due Date = Last Menstrual Period (LMP) + 280 days (40 weeks)
Or for ultrasound date:
Estimated Due Date = Ultrasound Date + (40 weeks - Gestational Age)
This calculation is based on the average length of pregnancy. Individual pregnancies may vary by a few days.
Example Calculation
If your last menstrual period was on January 1, 2023:
- Adding 280 days (40 weeks) gives an estimated due date of October 8, 2023
- This means you're in your 28th week of pregnancy on September 1, 2023
The calculator will show you the exact dates for each week of your pregnancy.
Frequently Asked Questions
How accurate is the estimated due date?
The estimated due date is based on the average length of pregnancy. Individual pregnancies may vary by a few days. An ultrasound provides a more precise gestational age.
Can I use this calculator if I had an ultrasound?
Yes, you can enter your ultrasound date and gestational age to get a more precise due date calculation.
What if my period was irregular?
If your periods are irregular, using the date of your last menstrual period may not be accurate. An ultrasound is recommended for precise tracking.
Can I track my baby's growth with this calculator?
This calculator focuses on the due date. For baby growth tracking, you would need additional medical information from your healthcare provider.