Calculate Your Estimated Due Date
Use this free expected birth date calculator to estimate your due date based on either your last menstrual period (LMP) or known conception date.
Note: This tool provides an estimate and does not replace medical advice or ultrasound dating from your healthcare provider.
What is an expected birth date?
An expected birth date (also called an estimated due date, or EDD) is the approximate day your baby may be born. Most pregnancies last about 40 weeks from the first day of the last menstrual period, but healthy deliveries can happen before or after that date.
How this calculator works
1) LMP method (most common)
The calculator starts from the first day of your last menstrual period and adds 280 days (40 weeks). If your cycle is longer or shorter than 28 days, it adjusts the estimate.
2) Conception date method
If you know your conception date, the calculator adds 266 days (38 weeks), which is the average pregnancy length from conception.
Why due dates are estimates, not guarantees
Only a small percentage of babies are born exactly on their due date. Birth often happens within a window around the EDD. Genetics, cycle variability, implantation timing, and natural labor patterns all influence actual delivery timing.
- Early ultrasound may shift your estimated date
- Irregular cycles can reduce date precision
- First pregnancies sometimes go beyond 40 weeks
- Medical decisions may change timing for safety
Pregnancy timeline at a glance
After calculating your expected birth date, it helps to think in milestones:
- Week 12: End of early first-trimester phase for many parents
- Week 14: Start of second trimester
- Week 28: Start of third trimester
- Week 37: Early term period begins
- Week 40: Estimated due date
Tips for using your due date well
Use it for planning, not pressure
Think of your due date as a planning anchor for appointments, leave requests, and baby prep—not as a strict deadline.
Track symptoms and appointments
A simple log of prenatal visits, ultrasounds, and symptoms can help you and your provider monitor progress clearly.
Stay flexible
It’s normal for plans to evolve near the end of pregnancy. Keep communication open with your care team.
Frequently asked questions
Can this calculator tell me the exact day I will give birth?
No. It provides a statistically informed estimate.
What if I have irregular periods?
Use the conception method if you know that date, and always confirm dating with your healthcare provider.
Should ultrasound override the calculator?
In many cases, yes—especially early ultrasound dating, which is often more precise than cycle-based estimates.
Final note
This expected birth date calculator is a convenient starting point. For medical care decisions, rely on professional prenatal guidance. A healthy pregnancy journey combines informed tools, routine checkups, and support from your care team.