Pregnancy Due Date & Date Calculator

Calculation Mode

From Last Menstrual Period (LMP) — most common From Conception Date From Known Due Date (reverse calculate)

Last Menstrual Period (LMP)

Average Cycle Length (days)

About the Pregnancy Due Date Calculator

This calculator determines your Estimated Due Date (EDD), current gestational age, trimester, and key pregnancy milestones using Naegele's Rule — the standard medical method for pregnancy dating. You can calculate from your Last Menstrual Period (LMP), a known conception date, or work backwards from an existing due date to find your LMP and conception window.

How to Use

Select your calculation mode — from LMP (most common), conception date, or known due date.
Enter the relevant date for your chosen mode.
If calculating from LMP, enter your average cycle length to adjust the due date for non-28-day cycles.
Click "Calculate Due Date" to see your EDD, gestational week, trimester, and milestone timeline.

Formula / Methodology

Naegele's Rule:
EDD = LMP + 280 days (40 weeks)

Cycle adjustment:
EDD += (Cycle Length − 28) days

From Conception:
LMP = Conception − 14 days
EDD = LMP + 280 days

Trimesters: T1=0–13w, T2=14–27w, T3=28–40w

Naegele's Rule assumes ovulation on day 14 of a 28-day cycle. For cycles longer or shorter than 28 days, the due date is adjusted by the difference, providing a more accurate EDD for non-standard cycles.

Understanding Your Results

Estimated Due Date (EDD) Your target delivery date — 40 weeks from LMP. Only about 5% of babies are born on the exact EDD; a range of ±2 weeks around this date is considered normal and healthy.

Current Trimester The first trimester (weeks 0–13) covers organ formation; the second (14–27) brings rapid growth and the anatomy scan; the third (28–40) is final development and preparation for birth.

Key Milestones Heartbeat detectable at week 6; anatomy scan at week 20; viability at week 24; full-term status begins at week 37. Milestones already passed are shown greyed out; upcoming ones within 14 days are highlighted.

Always Confirm with Your Healthcare Provider

Your EDD is an estimate based on calendar arithmetic. Ultrasound dating — particularly a first-trimester scan — provides a more accurate gestational age assessment. All pregnancy care, milestone monitoring, and delivery planning should be supervised by a registered OB/GYN or certified midwife. Do not rely solely on calculated dates for any medical decision.

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