📅 Due Date Calculator

Last Menstrual Period (LMP):

How It Works

Our pregnancy calculator uses Naegele's Rule to estimate your due date based on your Last Menstrual Period (LMP). Pregnancy typically lasts 280 days (40 weeks) from the first day of your LMP.

Enter the first day of your last period
We add 280 days to calculate your EDD
Track your current pregnancy week and day
See which trimester you're in

What is a Pregnancy Calculator?

A pregnancy calculator (also known as a due date calculator or gestational age calculator) is an essential online tool that estimates your expected delivery date based on your Last Menstrual Period (LMP). It helps expecting mothers track their pregnancy timeline, understand fetal development stages, and prepare for each trimester.

How Naegele's Rule Works:

Pregnancy is typically calculated as 280 days (40 weeks) from the first day of your last normal menstrual period. Our free pregnancy calculator adds 280 days to your LMP to estimate your due date. This method, known as Naegele's Rule, is based on a standard 28-day menstrual cycle and is widely used by healthcare providers worldwide.

Why Use Our Pregnancy Week Calculator?

Instant Results: Get your estimated due date in seconds
Trimester Tracking: Know exactly which trimester you're in
Gestational Age: Track weeks and days of pregnancy
No Signup Required: Completely free and private
Mobile Friendly: Works perfectly on all devices

Important Notes About Due Date Calculation

Due dates are estimates, not exact dates. Only about 5% of babies are born on their exact due date.
Consult your healthcare provider for accurate dating, especially if you have irregular cycles.
Ultrasounds can provide more precise dating in early pregnancy (first trimester).
Most babies arrive within 2 weeks of the estimated due date (between 38-42 weeks).
Cycle length matters: If your cycle is longer or shorter than 28 days, your due date may need adjustment.
IVF pregnancies use the embryo transfer date rather than LMP for dating.

Pregnancy Trimester Guide

Understanding your pregnancy trimesters helps you track fetal development and prepare for each stage. Use our pregnancy week calculator to determine which trimester you're currently in.

Weeks 1-13

First Trimester

Rapid fetal development begins. Morning sickness, fatigue, and breast tenderness are common. First ultrasound and prenatal visits typically occur. The baby's major organs begin forming.

Weeks 14-27

Second Trimester

Often called the "golden period." Quickening (feeling baby move) begins around week 18-20. Energy returns, and the baby bump becomes more visible. Anatomy scan usually done at week 20.

Weeks 28-40

Third Trimester

Baby descends into position for birth. Frequent kicks and movements felt. Preparation for delivery with breathing exercises and hospital bag packing. Final weeks bring anticipation and nesting instincts.

Frequently Asked Questions

How accurate is a pregnancy calculator? +

Pregnancy calculators using Naegele's Rule are generally accurate for women with regular 28-day cycles. However, due dates are estimates, and only about 5% of babies are born on their exact due date. Factors like irregular cycles, IVF conception, or unknown LMP can affect accuracy.

What if I don't know my last menstrual period? +

If you don't know your LMP, your healthcare provider can estimate your due date using an early ultrasound. The first-trimester ultrasound (between weeks 8-13) is the most accurate method for dating a pregnancy when the LMP is unknown.

Can I use this calculator for IVF pregnancies? +

For IVF pregnancies, due dates are calculated differently based on the embryo transfer date rather than LMP. Consult your fertility specialist for accurate dating, as IVF pregnancies often use the transfer date plus 266 days for blastocyst transfers.

What is gestational age vs. fetal age? +

Gestational age is calculated from the first day of your LMP (typically 2 weeks before conception), while fetal age is calculated from the actual date of conception. Our pregnancy week calculator shows gestational age, which is the standard measurement used by healthcare providers.

When should I take a pregnancy test? +

Most home pregnancy tests can detect pregnancy about 1 week after a missed period (approximately 3-4 weeks gestational age). For the most accurate results, wait until at least the first day of your missed period and use first-morning urine.

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