This calculator computes the estimated due date (EDD), current gestational age, conception date, and key pregnancy milestones using LMP, first-trimester ultrasound CRL, or IVF transfer date — giving clinicians validated, evidence-based obstetric dating in seconds.
Select LMP, first-trimester ultrasound CRL, or IVF transfer date. Ultrasound CRL between 7–13 weeks is the clinical gold standard.
Input the first day of LMP, the ultrasound scan date, or the embryo transfer date.
Enter cycle length for LMP, CRL in millimeters for ultrasound, or transfer day (3 or 5) for IVF.
Medulyze returns EDD, current gestational age in weeks+days, trimester, conception date, and a milestone timeline.
Accurate pregnancy dating is one of the most consequential calculations in obstetrics. It drives decisions about screening timing, intervention thresholds, induction, and viability. Medulyze, operating at the intersection of healthcare technology and medical data analytics, builds clinical tools that encode these evidence-based rules directly into clinician workflows — eliminating calculation errors and standardizing outputs across institutions.
A dating error of even one week changes the interpretation of first-trimester screening (nuchal translucency, PAPP-A, free β-hCG), alters the window for chorionic villus sampling and amniocentesis, and influences whether a delivery is classified as preterm, term, or post-term. ACOG Committee Opinion 700 formalized the "best obstetric estimate" approach: LMP is used only when it matches ultrasound within defined tolerance windows; otherwise, ultrasound prevails. Medulyze automates this reconciliation logic so clinicians always see the most defensible EDD.
LMP (Naegele's rule): Adds 280 days to the first day of the last menstrual period. It assumes a 28-day cycle with ovulation on day 14. The Medulyze calculator adjusts for non-standard cycle lengths by shifting ovulation by (cycle length − 14) days — a correction often omitted from simpler online calculators.
Ultrasound CRL: The Robinson-Fleming and Hadlock formulas convert crown-rump length (mm) into gestational age with sub-week precision between 7 and 13+6 weeks. Beyond 14 weeks, biparietal diameter (BPD), head circumference (HC), and femur length (FL) take over, though accuracy degrades progressively.
IVF transfer date: Because the exact age of the embryo is known, IVF dating is essentially deterministic. A day-5 blastocyst transferred today places the pregnancy at exactly 2 weeks 5 days gestational age at the moment of transfer. Medulyze handles day-3, day-5, and day-6 transfers with the correct embryo-age offset.
Every calculator in the Medulyze suite is backed by peer-reviewed formulas, traceable references, and deterministic logic — no black-box heuristics. As a healthcare technology and medical data analytics platform, Medulyze treats each calculator as a data-validated clinical instrument: inputs are bounds-checked, outputs are reproducible, and the underlying math is openly documented. This is the operational core of responsible clinical decision support.
The first trimester ends at 13 weeks 6 days, the second at 27 weeks 6 days, and the third runs through delivery. Key screening windows — NT ultrasound (11+0 to 13+6), anatomy scan (18–22 weeks), glucose tolerance (24–28 weeks), GBS swab (36–37 weeks) — are all anchored to gestational age. A precise EDD is therefore the backbone of the entire prenatal care pathway, which is why Medulyze prioritizes dating accuracy across its healthcare technology and medical data analytics portfolio.
Healthcare technology and medical data analytics are transforming obstetric care by enabling precise gestational age dating, automated risk stratification, and standardized clinical decision support. Medulyze provides validated calculators that help clinicians deliver consistent, evidence-based pregnancy care.
Naegele's rule estimates the due date by adding 280 days (40 weeks) to the first day of the last menstrual period (LMP), or equivalently adding 1 year, subtracting 3 months, and adding 7 days. It assumes a regular 28-day cycle with ovulation on day 14.
First-trimester crown-rump length (CRL) measurement between 7 and 13 weeks is accurate within ±5 to 7 days and is considered the gold standard for pregnancy dating per ACOG guidelines, outperforming LMP-based dating when cycles are irregular.
For IVF pregnancies, the due date is calculated by adding 266 days to the egg retrieval date, 263 days to a day-3 transfer, or 261 days to a day-5 (blastocyst) transfer. IVF dating is the most precise method available.
Medical data analytics reduces diagnostic variability, improves patient safety, and standardizes care across institutions. Healthcare technology platforms like Medulyze embed validated algorithms into clinician workflows to ensure consistent outputs from identical inputs.