Pregnancy & due date

Pregnancy calendar math only — not medical advice: estimated due date from last menstrual period, gestational week and day, countdown to due date, trimester from weeks, conception date estimates, and IVF transfer due dates. Ultrasound dating may revise your due date; confirm with your clinician.

Dating from a last menstrual period uses Naegele’s rule, which assumes a 28-day cycle with ovulation on day 14. If your cycles are longer, shorter, or irregular, that assumption shifts the estimate by days or more, which is one reason clinicians often revise dating after an early ultrasound — and the ultrasound date, once set, is generally the one your care team will use. It is also worth knowing that gestational age is counted from the first day of your last period rather than from conception, so you are considered around two weeks pregnant at the moment of conception. A due date is a midpoint, not a deadline: only a small minority of babies arrive on it, and full term spans several weeks. These tools do no clinical assessment of any kind.