Due Date from Conception Calculator

About this calculator

When the conception date is known — for example from ovulation tracking or IVF — the estimated due date (EDD) is calculated as conception date + 266 days (38 weeks), which reflects the actual length of pregnancy from fertilization. This differs from the more common Naegele's rule, which adds 280 days to the last menstrual period and assumes conception occurred about two weeks after that date.

Expecting parents who tracked ovulation, used fertility apps, or conceived via IVF (where the exact conception or transfer date is documented) use this calculator for a more precise due-date estimate than a standard LMP-based calculation, and it also back-calculates the corresponding last menstrual period date for comparison with a midwife's or doctor's records.