Pregnancy Due Date Calculator — Weeks, Trimester, Baby Development

Free online pregnancy due date calculator. Choose your method — last menstrual period (LMP, +280 days by Naegele's rule), known conception date (+266 days), or a recent ultrasound (date + reported gestational age) — and instantly see your estimated due date, current gestational age in weeks and days, trimester, baby's Chinese zodiac for the due- date year, and a short, factual fetal-development summary for every one of the 40 weeks (paraphrased from public ACOG and WHO guidance). Days and weeks until due update in real time, and the tool honors post-term arithmetic if your due date has passed. All calculation runs locally in your browser — the date you enter is never uploaded, never logged, never sent anywhere. This is an educational reference; it does not replace prenatal care or ultrasound dating by your obstetrician, which is more accurate than any formula.