Pregnancy Due Date Calculator
Track your journey. Estimate your due date and follow your baby's development.
Naegele's Rule
Naegele's rule is the standard method used to calculate the Expected Date of Confinement (EDC) or Due Date. It assumes a regular 28-day cycle.
Due Date = LMP + 1 Year - 3 Months + 7 Days
LMPFirst Day of Last Menstrual Period
ConstantAdds 280 days (40 weeks) total
Manual Calculation Example
Calculate the due date for an LMP of **January 1st**.
1
Add 7 Days
Add 7 days to the LMP.
January 1 + 7 = January 8
2
Subtract 3 Months
Go back 3 months.
January - 3 months = October (previous year)
3
Add 1 Year
Adjust the year forward.
October 8 (Next Year)
4
Result
The estimated due date.
October 8th
Pregnancy Milestones
1st Trimester
Weeks 1-12
The baby's major organs begin to form. The heart starts beating. Determining a due date is most accurate via ultrasound during this time.
2nd Trimester
Weeks 13-26
Many women feel the baby move ("quickening"). The gender can often be determined by ultrasound around week 20.
3rd Trimester
Weeks 27-40
The baby gains weight rapidly. Lungs mature significantly. By week 37, the pregnancy is considered "early term".
Frequently Asked Questions
How accurate is this calculator?
Calculators provide an estimate. Only about 4% of babies are born on their exact due date. Most are born within a week of it (before or after).
What is gestational age?
Gestational age is the time measured from the first day of your last menstrual period (LMP) to the current date. It is usually about 2 weeks older than the actual age of the fetus (conception age).
Why is pregnancy 40 weeks?
Pregnancy is counted from the LMP, which is about 2 weeks before conception. So the "40 weeks" includes these first two weeks before you were actually pregnant. The fetal development time is closer to 38 weeks.