Pregnancy and Women’s Health • Instant Result

Pregnancy Due Date Calculator

Calculate your estimated due date (EDD), current gestational age, and trimester milestones using Naegele’s clinical rule.

Enter Your Parameters

100% Client-Side Privacy: Inputs are processed in your browser and never stored.

Calculation Results

Ready

Enter values to calculate

Status Awaiting inputs

Understanding Your Result

The calculation generated by this tool provides an evidence-based assessment derived from established physiological and clinical equations. Use this measurement as an educational indicator alongside broader lifestyle variables, including overall dietary quality, resistance training, cardiovascular endurance, and routine medical checkups.

Mathematical Formula & Scientific Methodology

Naegele's Rule: Estimated Due Date (EDD) = First day of Last Menstrual Period (LMP) + 1 year - 3 months + 7 days (standard 280-day / 40-week gestation).

\text{EDD} = \text{LMP} + 280\text{ days}

Step-by-Step Example Calculation

If your LMP was January 10, 2026: Add 7 days (Jan 17), subtract 3 months (Oct 17, 2026) = Estimated Due Date is October 17, 2026.

Clinical Limitations & Nuances

Only about 4-5% of babies are born on their exact calculated due date. 90% deliver within two weeks before or after. Confirm via first-trimester ultrasound.

Frequently Asked Questions

How accurate is a due date calculated from LMP?

LMP calculations provide a close estimate for women with regular 28-day cycles. A first-trimester crown-rump length ultrasound provides the clinical gold standard for dating.

When does each trimester begin and end?

First Trimester: Conception to Week 13. Second Trimester: Week 14 to Week 27. Third Trimester: Week 28 to Delivery (~Week 40).

Medically Reviewed Content