Pregnancy Calculator
Find your estimated due date, see how many weeks and days pregnant you are today, and explore your customized fetal development milestones.
Choose Your Dedicated Calculator
Each tool is specifically designed for distinct clinical questions with zero fluff.
1. Pregnancy Calculator
Our primary authority tracker. Features live Pregnancy Now tracking, gestational week & day counting, trimester breakdowns, and visual milestones.
2. Due Date Calculator
Compare estimated delivery dates across LMP, conception, and ultrasound biometry. Includes cycle length adjustments (20–45 days) and delivery window distributions.
3. Conception Date Calculator
Work backward from your estimated due date or last period to determine when fertilization likely took place and view your 6-day fertile window.
How Pregnancy Calculations Work
Evidence-based standards, biological timing, and why due dates are estimates.
The 280-Day Clinical Convention (Naegele's Rule)
Because the exact moment of fertilization is rarely known with certainty, obstetricians universally standardize pregnancy dating from the first day of the last menstrual period (LMP). Assuming a 28-day cycle with ovulation on day 14, human pregnancy lasts approximately 280 days (40 completed weeks) from LMP, or 266 days (38 weeks) from fertilization.
Cycle Length Variations Matter
Natural human menstrual cycles range from 20 to 45 days. The follicular phase (time before ovulation) varies widely, while the luteal phase (post-ovulation) remains relatively fixed at ~14 days. If your cycle is 35 days, you likely ovulated on day 21, shifting your due date 7 days later than standard charts indicate.
Due Dates Are Estimates, Not Expiration Dates
Studies published in peer-reviewed obstetrics journals demonstrate that only 4–5% of infants are born on their exact calculated EDD. However, approximately 80% deliver within the normal full-term window between 37 weeks 0 days and 41 weeks 6 days.
Featured Pregnancy Guides
Medically referenced guides on clinical due dates, ultrasound dating, and gestational milestones.
How Is My Due Date Calculated?
Learn the mathematical mechanics of Naegele's Rule, Mittendorf-Williams models, and ultrasound reconciliation.
How Accurate Are Due Date Estimates?
What clinical data says about spontaneous delivery timing and why due dates represent a window.
What Happens in Each Trimester?
Comprehensive breakdown of organ development, viability landmarks, and bodily maternal changes.
Our Commitment to Accuracy & Transparency
NurtureCalc exists to provide transparent, scientifically grounded pregnancy calculations without paywalls, hidden algorithms, or invasive data harvesting. We cite authoritative medical institutions including the American College of Obstetricians and Gynecologists (ACOG), the CDC, and the NIH.