Estimated Due Date Calculator
Calculate your estimated due date (EDD) using the first day of your last menstrual period (LMP).
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Estimated Due Date (EDD)
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Based on Naegele’s Rule (LMP + 280 days)
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Using the Pregnancy & Due Date Calculator
Knowing your **Estimated Due Date (EDD)** is the first step in pregnancy planning. This **Pregnancy Calculator** uses the universally accepted method based on the first day of your **Last Menstrual Period (LMP)** to give you an estimate of when your baby will arrive.
Naegele’s Rule Explained
Most pregnancies last about **40 weeks** (or 280 days) from the first day of your LMP. Naegele’s rule calculates the EDD by adding 280 days to the date of your LMP. This assumes a 28-day menstrual cycle.
$$\text{EDD} = \text{LMP} + 280 \text{ days}$$
Trimester Breakdown
Pregnancy is divided into three trimesters, each marking important developmental milestones:
- **First Trimester:** Week 1 to the end of Week 13.
- **Second Trimester:** Week 14 to the end of Week 27.
- **Third Trimester:** Week 28 to the end of the pregnancy (Week 40).
Frequently Asked Questions (FAQ)
How accurate is the LMP method?
The LMP method is a good estimate, but its accuracy depends on having a **regular 28-day cycle** and knowing the exact LMP date. Your healthcare provider will confirm and refine the due date using ultrasound scans, especially early in the first trimester.
What if my cycle is irregular?
If your menstrual cycle is irregular, the LMP method is less reliable. Your doctor will rely more heavily on early **ultrasound scans** (which measure the size of the fetus) to determine a more accurate EDD.