Pregnancy Due Date Calculator — Gestational Age & Milestone Timeline

Last reviewed: April 2026

This pregnancy due date calculator uses Naegele's Rule — the standard method used by OB/GYN providers — to estimate your baby's due date from the first day of your last menstrual period (LMP). The standard calculation assumes a 28-day cycle; if your cycle is longer or shorter, this calculator adjusts the conception estimate and due date accordingly. The tool outputs your estimated due date, current gestational age (if already pregnant), estimated conception window, trimester end dates, and a visual milestone timeline with key developmental and clinical checkpoints. All calculations are date-only estimates — actual due dates are confirmed by early ultrasound, which remains the most accurate dating method. Use this tool for general planning reference only.

Calculate Your Estimated Due Date

Please select a valid LMP date (within the past 10 months).
Please enter a cycle length between 21–35 days.

🔒 Your numbers stay in your browser — nothing is sent to any server.

Estimated Due Date
—
40 weeks from LMP
Current gestational age: — weeks — days
LMP Date
—
Start of gestational count
Est. Conception Window
—
~LMP + (cycle ÷ 2) days
End of 1st Trimester
—
Week 13+0
End of 2nd Trimester
—
Week 27+0
Full Term
—
Week 37+0
Estimated Due Date
—
Week 40+0 (EDD)
First Trimester
Weeks 1 – 13
—
Second Trimester
Weeks 14 – 27
—
Third Trimester
Weeks 28 – 40
—

🗓 Pregnancy Milestone Timeline

⚕ Reference Only: This due date estimate is based on Naegele's Rule from your reported LMP and may differ from your clinically confirmed due date. Early ultrasound (ideally before 14 weeks) is the most accurate method for pregnancy dating. Always confirm your due date and pregnancy milestones with your OB/GYN or midwife.

Helpful pregnancy tracking resources:

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Sources & Methodology

Formula: Naegele's Rule — Estimated Due Date (EDD) = First day of last menstrual period (LMP) + 280 days (40 weeks), adjusted for cycle length relative to the standard 28-day cycle. Conception date estimated as LMP + 14 days (average ovulation day).
Source: Standard obstetric dating method; American College of Obstetricians and Gynecologists (ACOG) Committee Opinion on methods for estimating the due date. Note: First-trimester ultrasound dating is more accurate than LMP-based calculation, particularly when cycle length is irregular.

Last reviewed: April 2026