What is an estimated due date?
An estimated due date is an approximate date when a baby may be born. A traditional calculation starts with the first day of the last menstrual period and estimates about 280 days, or 40 weeks, of pregnancy.
PREGNANCY CALCULATOR
Pregnancy Due Date Calculator
Estimate your due date, gestational age, estimated conception date, and pregnancy stage from the first day of your last menstrual period or a known due date.
Enter the first day of your most recent menstrual period.
Enter a date to calculate
Enter the first day of your last menstrual period or an estimated due date to see your pregnancy timeline.
PREGNANCY BASICS
Pregnancy Calculation Basics
Understanding how due dates, gestational age, and conception dates relate can help you interpret your pregnancy timeline.
How is conception estimated?
For a regular menstrual cycle, ovulation often occurs about two weeks before the next period. Conception is therefore commonly estimated at around two weeks after the first day of the last menstrual period.
Why is pregnancy dated from the last period?
Clinical gestational age is generally counted from the first day of the last menstrual period rather than from the actual day of fertilization. Therefore, gestational age is usually about two weeks greater than the time since conception.
What are the three trimesters?
Pregnancy is commonly divided into the first, second, and third trimesters. Fetal development and maternal changes differ across these stages, and prenatal care changes as pregnancy progresses.
Is the due date exact?
A due date is an estimate, not a guaranteed birth date. Differences in menstrual cycle length and ovulation timing can affect the calculation.
When should I talk to a healthcare professional?
A pregnancy calculator only provides date estimates and cannot replace prenatal care or medical evaluation. Seek professional medical advice for concerning symptoms such as unusual bleeding, significant abdominal pain, severe headache, or concerns about fetal movement.
HOW IT WORKS
How the Due Date Is Calculated
Estimated due date ≈ first day of LMP + 280 days
This is a commonly used pregnancy dating method based on an assumed 28-day menstrual cycle and ovulation around day 14.
- A standard pregnancy is commonly estimated as 40 weeks.
- Gestational age is counted from the first day of the last menstrual period.
- The estimated due date may be adjusted based on cycle length, ovulation timing, and prenatal assessment.
FAQ
Pregnancy Due Date FAQ
How is the due date calculated?
A common method is to count 280 days, or 40 weeks, from the first day of the last menstrual period to estimate the due date.
Is pregnancy counted from the date of conception?
Usually not. Clinical gestational age is generally counted from the first day of the last menstrual period, so it is typically about two weeks greater than the time since conception.
Can I calculate a due date if my periods are irregular?
You can still make an initial estimate, but calculating from the last menstrual period may be less accurate when cycles are irregular. A healthcare professional can provide a more appropriate assessment.
How accurate is a pregnancy due date calculator?
A due date calculator provides an estimate rather than an exact birth date. Ovulation timing, menstrual cycle length, and prenatal assessment can all affect the estimated due date.
Important note
This tool is intended only to estimate pregnancy dates and an estimated due date. It is not intended for diagnosis or treatment and does not replace professional medical advice. Consult a qualified healthcare professional if you have questions about gestational age, your due date, or pregnancy symptoms.