Free Pregnancy Calculator Online
Use this free pregnancy calculator to estimate your due date, find your current pregnancy week, and track key milestones through all three trimesters — all online and completely free.
Estimated Due Date
Enter your LMP above
How the Pregnancy Calculator Works
This pregnancy calculator uses Naegele's rule — the standard method used by doctors worldwide. It takes the first day of your last menstrual period (LMP), adds 280 days (40 weeks), and adjusts for your actual cycle length. A 28-day cycle assumes ovulation on day 14. If your cycle is longer or shorter, the pregnancy calculator shifts the estimated ovulation date and recalculates your due date accordingly.
Gestational age counts from LMP, not conception. So when the pregnancy calculator says "6 weeks pregnant," the embryo is actually about 4 weeks old. This is the universal convention used in prenatal care and is how your doctor will track your progress.
Understanding Your Trimesters
First Trimester (Weeks 1–12)
Major organ systems form. The heart starts beating around week 6. Morning sickness peaks between weeks 8 and 10 for most women. By week 12, the risk of miscarriage drops significantly.
Second Trimester (Weeks 13–26)
Often called the "golden period." Nausea typically fades, energy returns. The anatomy scan around weeks 18–20 checks organ development. Most women feel first movements (quickening) between weeks 16 and 22.
Third Trimester (Weeks 27–40)
The baby gains most of its birth weight. Lungs mature around week 34–36. Full term is reached at week 37. Prenatal visits increase to weekly as you approach your estimated due date.
Key Pregnancy Milestones to Track
Week 6
Heartbeat Detectable
The embryo's heart begins beating. Often visible on early ultrasound.
Week 12
End of First Trimester
Miscarriage risk drops sharply. Many parents share the news around this point.
Week 20
Anatomy Scan
Detailed ultrasound checks all major organs and structures. Halfway mark.
Week 37
Full Term
Baby is considered full term. Labor could begin any day from here.
Why Due Dates Are Estimates
The average pregnancy lasts 280 days from LMP, but healthy pregnancies range from 37 to 42 weeks. Factors like first vs. subsequent pregnancies, maternal age, and genetics all influence timing. A pregnancy calculator gives you the best statistical estimate — think of it as the center of a two-week window, not a fixed appointment. Your healthcare provider may adjust the date based on early ultrasound measurements, which are accurate to within 3–5 days in the first trimester. This free online pregnancy calculator is a starting point for planning, not a medical prediction.
Frequently Asked Questions
Disclaimer: This free online pregnancy calculator is for informational and educational purposes only. It provides estimates based on standard formulas and does not replace professional prenatal care. Always consult your healthcare provider for medical advice regarding your pregnancy. This free tool is available online 24/7.
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