About

Estimating delivery dates relies on Naegele's Rule, which adds 280 days to the first day of the last menstrual period (LMP). While ultrasounds provide the most accurate dating, this calculation serves as the standard initial estimation used by obstetricians. This tool calculates the Estimated Due Date (EDD), current gestational age (weeks and days), and the remaining time in the pregnancy. It maps the current week to fetal size comparisons using recognizable objects (fruits/vegetables) and highlights key physiological milestones such as heartbeat detection or viability.

Formulas

The calculation assumes a standard 28-day cycle. The Estimated Due Date (EDD) is derived from the Last Menstrual Period (LMP):

EDD = LMP + 280 days

Current Gestational Age is calculated as:

Current Week = floor(Days Since LMP7)

Reference Data

Trimester	Weeks Range	Key Developments
First	Weeks 1 - 12	Organogenesis, heartbeat detectable, neural tube closes.
Second	Weeks 13 - 26	Movement felt (quickening), gender visible, hearing develops.
Third	Weeks 27 - 40+	Lungs mature, rapid weight gain, head engages for labor.

Frequently Asked Questions

40 weeks is roughly 10 lunar months (28 days each). This precise counting avoids confusion, as calendar months vary in length. A full-term pregnancy is considered anywhere from 37 to 42 weeks.

The standard formula assumes a 28-day cycle with ovulation on day 14. For irregular cycles, the date of conception (if known) or an early dating ultrasound is required for accuracy.

Viability is the point at which a fetus has a chance of survival outside the womb. This is generally considered to be around 24 weeks gestation, though intensive medical care is required.