Obstetrics and gynaecology
Gestational Age & EDD
Estimated due date from last menstrual period.
Gestational Age & EDD calculator
Result
10+0weeks
~30.0 weeks until EDD (Naegele's rule)
EDD by Naegele = LMP + 280 days. Adjust if cycles ≠ 28 days.
How to use it
- 1
Confirm LMP by ultrasound. US dating preferred if ≥5 days discrepancy in first trimester. CRL most accurate <14 weeks.
- 2
EDD = LMP + 280 days. 40 weeks from first day of LMP (Naegele's rule).
- 3
Adjust for cycle length. Cycle ≠ 28 days: add (cycle length − 28) days to EDD.
When to use it
- Antenatal booking
- EDD determined at booking scan (11–13+6 weeks) — US dating used if CRL-based EDD differs from LMP by ≥5 days.
- Post-dates monitoring
- ≥40 weeks: membrane sweep offered. ≥41 weeks: induction discussed.
- Pre-term birth risk
- < 37+0 = pre-term. < 34+0 = very pre-term. < 28+0 = extreme pre-term.
A reference for clinicians and students, not medical advice. A score supports a decision; it does not make one. Check every result against the patient in front of you and your local protocol.
At a glance
- Specialty
- Obstetrics and gynaecology
- Inputs
- 1
- Type
- Formula
