Is the Due Date Calculator accurate?

This tool uses the same formulas used in clinical practice by healthcare professionals, validated against research data from peer-reviewed studies. For most adults, results are accurate within the typical clinical margin of error for the calculation type. Individual factors including genetics, medications, and health conditions can affect your personal result. Always discuss health calculations with a qualified healthcare provider before making significant changes.

Is my health data stored when I use this calculator?

No personal data is ever transmitted, stored, or shared. All calculations happen entirely within your browser using JavaScript. When you close the page, your inputs disappear permanently. This privacy-first design is essential for sensitive health information.

How often should I recalculate my due date?

For tracking purposes, recalculating monthly gives the most meaningful trend data without the noise of daily fluctuations. If your weight, activity level, or health status changes significantly, recalculate at that time. For acute health concerns, consult a healthcare provider rather than relying on a self-assessment calculator.

Can I use the Due Date Calculator on my phone?

Yes — this calculator is fully responsive and works on all devices including iPhone, Android, iPad, and desktop computers. No app download is required. The interface automatically adjusts to your screen size.

What units does the Due Date Calculator support?

The calculator supports both US customary units (pounds, feet, inches) and metric units (kilograms, centimeters). Use the toggle or unit selector to switch between systems. Results are shown in both units where relevant.

Who should I consult if my due date result is concerning?

Consult your primary care physician for any health metric result that falls significantly outside the healthy range. For nutrition-related results, a registered dietitian (RD) is the appropriate specialist. For fitness-related results, a certified personal trainer or exercise physiologist can provide personalized guidance.

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Health

Pregnancy Due Date Calculator

Calculate your estimated due date from LMP or conception date. Full pregnancy timeline and milestone tracker.

Pregnancy Details

Calculate From

First Day of Last Period

Cycle Length

days

Estimated Due Date

November 30, 2026

237 days remaining

Currently

6w 0d

Trimester 1

Conception

March 9, 2026

Pregnancy Timeline & Milestones

✅

Week 6

Heartbeat detectable

April 6, 2026

8wks

Week 8

First ultrasound possible

April 20, 2026

10wks

Week 10

NIPT genetic testing

May 4, 2026

12wks

Week 12

End of highest miscarriage risk

May 18, 2026

16wks

Week 16

Gender can be determined

June 15, 2026

20wks

Week 20

Anatomy scan ultrasound

July 13, 2026

24wks

Week 24

Viability milestone

August 10, 2026

28wks

Week 28

Third trimester begins

September 7, 2026

32wks

Week 32

Baby is head-down usually

October 5, 2026

36wks

Week 36

Weekly checks begin

November 2, 2026

37wks

Week 37

Full-term (safe delivery)

November 9, 2026

40wks

Week 40

Due date

November 30, 2026

Complete Guide

Due Date Calculator -- Complete USA Guide 2026

The Due Date Calculator provides instant, evidence-based results using clinically validated formulas from leading health organizations. Every calculation runs locally in your browser — no data stored, no account needed, works on any device.

Understanding your due date metrics is an important component of proactive health management. This tool gives you the same calculations used in clinical and research settings, with reference ranges and health context that help you understand what your result actually means — and what actionable next steps are appropriate.

Whether you are preparing for a healthcare appointment, tracking progress in a wellness program, or simply curious about this aspect of your health, this calculator provides a reliable, science-backed starting point.

Combine with our BMI Calculator, our TDEE Calculator, and our Calorie Calculator for a comprehensive health assessment.

🔬 How This Calculator Works

The standard estimated due date (EDD) calculation uses Naegele's Rule: EDD = first day of LMP + 280 days (40 weeks). This assumes a 28-day cycle with ovulation at day 14 — the rule adds 7 days to LMP then counts forward 9 months. For cycles different from 28 days, the EDD is adjusted: add (cycle length - 28) days.

For IVF pregnancies: fresh day-5 blastocyst transfer: EDD = transfer date + 261 days (37 weeks); day-3 transfer: EDD = transfer date + 263 days; frozen-thawed blastocyst: EDD = transfer date + 261 days (adjusted to calendar date of natural cycle ovulation for non-synchronized FET).

Ultrasound EDD is calculated from crown-rump length (CRL) measured at 8-14 weeks using Hadlock's formula: GA (days) = 42.859 + 1.599 × CRL(mm) − 0.00041 × CRL(mm)². Ultrasound EDD is more accurate than LMP-based dating when measured before 14 weeks.

✅ What You Can Calculate

Evidence-based clinical formulas

Uses peer-reviewed, validated formulas from major health organizations — the same calculations trusted by healthcare professionals in clinical and research settings.

Instant real-time results

Results update as you type — no button to click. Explore multiple scenarios in seconds to understand how changes affect your result.

Complete data privacy

All calculations run entirely in your browser. No personal health data is transmitted, stored, or shared anywhere — ever.

Health context included

Beyond a raw number, results include reference ranges, health category classification, and guidance from major health organizations on what your result means.

Works on all devices

Fully responsive design works perfectly on phone, tablet, and desktop. No app download required — just open in your browser.

Completely free

No signup, no subscription, no premium features. Every calculation and all health context is permanently free for every user.

🎯 Real Scenarios & Use Cases

Annual health monitoring

Calculate and record key health metrics annually to build a personal health history that reveals meaningful trends and supports proactive health decisions over time.

Doctor appointment preparation

Arrive at medical appointments with your own calculations already done, enabling more focused and productive conversations about your health with your healthcare provider.

Wellness program participation

Track progress in employer wellness programs or personal health initiatives with objective, calculated metrics that are meaningful and evidence-based.

Health education and research

Students, educators, and researchers in health and nutrition fields use these tools to apply classroom formulas to real-world calculations and develop genuine health literacy.

💡 Pro Tips for Accurate Results

If your ultrasound due date differs from your LMP due date by more than 5-7 days (before 14 weeks), most OBs will adjust the due date to the ultrasound estimate — ultrasound crown-rump length before 14 weeks is the most accurate dating method available.

Due dates are estimates with a wide confidence interval — only 5% of babies are born on their exact due date. The normal range is 38-42 weeks (10 days before to 2 weeks after the EDD). Full-term delivery is 39-40 weeks; early term is 37-38 weeks; late term is 41 weeks; post-term is 42+ weeks.

Planning: use the trimester breakdown and milestone dates for scheduling key appointments. First trimester screening (nuchal translucency ultrasound + bloodwork) should be scheduled between 11-14 weeks; anatomy scan at 18-22 weeks; glucose tolerance test at 24-28 weeks.

🔢 Data Sources & Methodology

The Naegele's Rule is named after German obstetrician Franz Karl Naegele who described it in 1812 — making it over 200 years old and still the primary due date calculation method in clinical practice. The 40-week gestational period was originally observed empirically and has been validated by large cohort studies. A 2013 study by Jukic et al. (Human Reproduction) analyzed 125 natural conceptions with precisely known fertilization dates and found mean duration from ovulation to delivery was 268 days, with enormous individual variation (228-298 days) — confirming that due dates have wide uncertainty regardless of calculation method.

🏁 Bottom Line

Your due date calculation gives you a meaningful, personalized number grounded in validated science — far more useful than generic population guidelines that may not apply to your specific situation, body, and health history.

Use this result as one component of your complete health picture. Combine it with regular monitoring of other key metrics, professional medical guidance when results fall outside normal ranges, and consistent healthy behaviors that address the factors most within your control.

Explore our BMI Calculator, our Body Fat Calculator, our Calorie Calculator, and our TDEE Calculator for a complete health assessment.

Frequently Asked Questions

This calculator uses validated clinical formulas and evidence-based reference ranges to estimate your due date based on your inputs. All calculations run locally in your browser for complete privacy. Results include your personal estimate plus health context from major medical organizations including the CDC, NIH, and American Heart Association to help you understand what the number means for your health.