Gestational Age & EDD Calculator

1 What is the Gestational Age & EDD Calculator?

The Gestational Age & EDD Calculator estimates a pregnancy's due date and current gestational age using five different dating methods — last menstrual period (LMP), dating ultrasound, a known EDD, IVF/ART embryo transfer date, or a known conception date. Once a due date is set, it tracks trimester progress, shows expected fetal development for the current gestational week, and generates a calendar of antenatal surveillance milestones calculated forward from the estimated LMP.

2 When to use it

Establishing an estimated due date (EDD) at a first antenatal visit from LMP, a dating ultrasound, or an already-known EDD
Dating a pregnancy conceived via IVF/ART using the embryo transfer date and embryo age (Day 5, Day 3, or Day 0)
Tracking gestational age, trimester, and days remaining to term through pregnancy
Planning the timing of routine antenatal tests and interventions (NT scan, anomaly scan, glucose screening, Tdap, Rho(D) immunoglobulin, GBS screening)
Reviewing expected fetal development at a specific gestational week
Calculating gestational age on any specific calendar date, such as a past or future visit

3 Formula & method

The calculator offers five dating methods, each with its own formula shown in the app: LMP method — Corrected LMP = LMP + (cycle length − 28), then EDD = corrected LMP + 280 days; Ultrasound method — EDD = scan date − GA at scan + 280 days; Known EDD method — LMP = EDD − 280 days (back-calculated); IVF/ART method — EDD = embryo transfer date + 261 days for a Day 5 blastocyst transfer, + 263 days for a Day 3 transfer, or + 266 days for a Day 0 (fresh retrieval) transfer; Conception-date method — EDD = conception date + 266 days, LMP = conception date − 14 days. From the resulting LMP, the app also builds a calendar of antenatal windows (e.g. NT scan 11w0d–13w6d, anomaly scan 18w–22w, glucose screen 24w–28w, Rho(D) at 28w, Tdap 27w–36w, GBS screen 36w–37w6d) plus condition-specific antenatal-testing start points such as 32 weeks for monochorionic-diamniotic twins, poorly controlled diabetes, or a prior stillbirth, per the app's own list.

ACOG Practice Bulletins
RCOG Green-top Guidelines
NNF India
IAP India Guidelines

4 Frequently asked questions

What dating methods does this EDD calculator support?

Five: last menstrual period (LMP) with cycle-length correction, dating ultrasound, a previously known EDD, IVF/ART embryo transfer date, and a known conception date.

How does IVF/ART dating differ from LMP dating?

EDD is calculated directly from the embryo transfer date, adding 261 days for a Day 5 blastocyst transfer, 263 days for a Day 3 transfer, or 266 days for a Day 0 (fresh retrieval) transfer.

What if my cycle length isn't 28 days?

The LMP method corrects for this: Corrected LMP = LMP + (cycle length − 28), before adding 280 days to get the EDD.

What antenatal milestones does the calculator flag?

It generates a calendar of common surveillance windows — NT scan, anomaly scan, glucose screening, Rho(D) immunoglobulin, Tdap vaccination, and GBS screening — calculated from the estimated LMP. The app describes this as a workflow aid to be used with clinician judgment and current practice guidance.

What guidelines does the tool reference?

The app's own disclaimer cites ACOG Practice Bulletins, RCOG Green-top Guidelines, NNF India, and IAP India Guidelines, and states results should be used with clinical judgment.

5 Related tools

For qualified clinicians. This page and the PediAid app are a clinical aid only. Calculations and reference data must be verified against the patient's clinical context, the source guideline and your local protocols before any treatment decision is made.