Pregnancy Due Date Calculator

What is Estimated Due Date (EDD)?

An Estimated Due Date (EDD) projects the expected calendar date of delivery, calculated 40 weeks (280 days) from the first day of your Last Menstrual Period (LMP).

How Does the Pregnancy Due Date Calculator Work?

The tool uses clinical Naegele's Rule: EDD = LMP Date + 1 Year - 3 Months + 7 Days. It adjusts for cycle length variations when specified.

Step-by-Step Gestational Calculation

• Step 1: Input first day of Last Menstrual Period (LMP).
• Step 2: Adjust average cycle length (default 28 days).
• Step 3: Calculate current gestational week and milestone trimester dates.

Edge Cases & IVF/Ultrasound Adjustments

For pregnancies conceived via IVF, due date is calculated from embryo transfer date (e.g. Transfer Date + 263 days for Day 5 embryos). First trimester ultrasound crown-rump length (CRL) measurements override LMP estimates when discrepancies exceed 5 days.

Trimester Timeline Breakdown

• First Trimester: Weeks 1 through 12 (critical organogenesis).
• Second Trimester: Weeks 13 through 27 (fetal growth and movement).
• Third Trimester: Weeks 28 through 40+ (final maturation).

When Do You Need This Calculation?

• Prenatal Scheduling: Timing OB/GYN checkups, anomaly scans, and glucose screening.
• Maternity Planning: Coordinating leave policies and postpartum support alongside our Time Between Dates Calculator.

How Gestational Age Differs From Chronological Age

Gestational age measures weeks since LMP, whereas Adjusted Age Calculator evaluates premature infants post-birth, and Age Calculator calculates solar calendar age after birth.