Calculator · Women's / obstetric

EDD & gestational age (from LMP)

Estimated due date and current gestation from the last menstrual period (Naegele’s rule).

What it is for

Confirming pregnancy dates before the dating scan; antenatal booking. A USS at 11–14 weeks supersedes LMP dating.

Use the working calculator

The working EDD & gestational age (from LMP) calculator is on our calculators page. It is free and needs no account. Enter the values and it shows the result with the reading that goes with it.

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What you enter

The calculator asks for 2 items.

  • First day of last menstrual period (LMP) (a date)Reliable, certain dates only.
  • Usual cycle length (days)Optional — defaults to 28.

How the result is read

The result is shown as Result. Formula: EDD = LMP + 280 days (+ adjustment for cycle length ≠ 28)

The calculator reports one of these readings, with the action that goes with it: LMP is in the future; Past dates / post-term range; Term —; Post-term —.

Sources

These are the sources the calculator cites. Check the current version before relying on a threshold.

Related

PUQE (nausea/vomiting of pregnancy)Severity of nausea & vomiting in pregnancy (3 items, 3–15).Gestational age (from EDD)Current gestation and trimester from a known estimated due date (e.g. the dating-scan EDD).CHA₂DS₂-VAScStroke risk score in non-valvular AF.HAS-BLEDMajor bleeding risk on anticoagulation for AF.ORBITAlternative bleeding risk score for AF — may outperform HAS-BLED.All calculators60 clinical scores and tools

For qualified clinicians. A score supports a clinical decision and does not make it: check the inputs, read the cited source, and use the tools in your clinical system for patient care where one is provided.