Calculators/Estimated Due Date (EDD)

Estimated Due Date (EDD) Calculator

Due date and gestational age by Nägele’s rule from LMP

First day of last menstrual period — day

First day of last menstrual period — month

First day of last menstrual period — year

Equation & limitations

Equation: EDD = LMP + 280 days (Nägele’s rule). Gestational age = calendar days between LMP and the reference date ÷ 7.
Version: Nägele’s rule (280 days from a 28-day-cycle LMP)
Source: Nägele’s rule as commonly applied in obstetric practice. (A reappraisal: Baskett TF, Nagele F. Naegele’s rule: a reappraisal. BJOG. 2000;107:1433–1435.)
Appropriate in: Singleton pregnancies dated from a certain LMP with a regular ~28-day cycle. Ultrasound dating is preferred when available.
Limitations: Assumes a 28-day cycle with ovulation at day 14; irregular cycles, recent oral-contraceptive use, or uncertain LMP make it unreliable.
EDD should be confirmed/adjusted by early ultrasound; the tool cannot substitute for that.
Gestational-age display depends on the reference date supplied (today when run in the browser).

For educational use. Results support, and do not replace, clinical judgement — check them against the patient and local guidelines.