Calculate Your Expected Date of Delivery (EDD)
Use this expected date of delivery calculator to estimate your pregnancy due date based on your last menstrual period, conception date, or IVF transfer date.
This calculator is for educational use and does not replace medical advice from your obstetric provider.
What is an expected date of delivery?
The expected date of delivery (EDD), also called the estimated due date, is the date a pregnancy is projected to reach 40 weeks of gestation. It is a planning tool, not an exact prediction. Most babies are born within a range of dates rather than on one exact day.
In clinical practice, providers use the EDD to schedule prenatal visits, track fetal growth, time screening tests, and identify pregnancies that may be preterm or post-term. This expected date of delivery calculator provides an estimate using common obstetric formulas.
How this calculator estimates your due date
1) Last Menstrual Period (LMP) method
If you know the first day of your last menstrual period, this is the most common starting point. The calculator adds 280 days (40 weeks), with an adjustment for cycle length if your cycle is shorter or longer than 28 days.
- Standard cycle (28 days): EDD = LMP + 280 days
- Longer cycle: due date shifts later
- Shorter cycle: due date shifts earlier
2) Conception date method
If you know your conception date (for example, with tracked ovulation or insemination), the calculator adds 266 days (38 weeks) to estimate your EDD. This method can be useful when ovulation timing is known with confidence.
3) IVF transfer method
IVF dating is often very precise because the transfer date and embryo age are known. The tool calculates EDD from transfer date and embryo development day. This approach is commonly used in fertility clinics and obstetric follow-up care.
How accurate is a due date?
Even with excellent dating, birth rarely occurs exactly on the estimated date. In uncomplicated pregnancies, a full-term birth can occur from 37 to 42 weeks. That means the EDD is best understood as the center of a realistic time window, not a strict deadline.
- Only a small percentage of babies arrive exactly on their due date.
- First pregnancies are often slightly longer on average.
- Ultrasound measurements may refine dates, especially in early pregnancy.
Why your provider might change your due date
Sometimes the estimated date changes after an early ultrasound. If fetal measurements differ significantly from LMP-based dating, clinicians may update the EDD to improve care planning and timing of tests.
This is normal and does not automatically indicate a problem. It usually reflects improved precision in pregnancy dating.
How to use your EDD in real life
- Plan prenatal appointments and key screening windows.
- Track trimester transitions and milestones.
- Estimate when maternity/paternity leave may begin.
- Prepare your support system and delivery logistics.
- Discuss any concerns promptly with your clinician.
Important medical note
This expected date of delivery calculator does not diagnose conditions and cannot replace individualized obstetric care. Always rely on your healthcare professional for decisions regarding prenatal testing, labor signs, reduced fetal movement, bleeding, severe pain, or any urgent symptoms.
Frequently asked questions
Is EDD the same as due date?
Yes. EDD stands for expected date of delivery and is commonly used interchangeably with estimated due date.
Can I calculate due date if my periods are irregular?
You can estimate it, but irregular cycles reduce precision with LMP dating. Early ultrasound and provider assessment are especially important in that case.
If my EDD passes, is something wrong?
Not necessarily. Many healthy pregnancies continue beyond the due date. Your provider will monitor fetal well-being and discuss induction timing if needed.
Bottom line
A due date estimate helps you stay organized and informed throughout pregnancy. Use this calculator as a practical starting point, then confirm and personalize your timeline with your prenatal care team.