👶 Pregnancy & Baby

Baby Due Date Calculator

Find your baby's due date using Naegele's rule as recommended by ACOG. Generate a personalized pregnancy milestone timeline with key dates for each trimester.

First Day of Last Menstrual Period (LMP) The first day of your last period ACOG recommends calculating EDD by adding 280 days to LMP[reference:0].

Average Cycle Length (days) Your typical menstrual cycle length For irregular cycles, ACOG recommends adjusting by adding the cycle difference[reference:1].

Estimated Due Date

📅Due Date
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40 weeks from LMP

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Current Week

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Weeks Remaining

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Conception Date

Estimated date of conception

Trimester Dates

First Trimester

Weeks 1–12

Second Trimester

Weeks 13–26

Third Trimester

Weeks 27–40

Pregnancy Milestone Timeline

📋 Clinical References:

ACOG — American College of Obstetricians and Gynecologists recommends calculating EDD by adding 280 days to LMP[reference:2].
Naegele's Rule — Standard method since the 1800s: add 7 days to LMP and subtract 3 months[reference:3].
First-trimester ultrasound — Recommended before 14 weeks to confirm or adjust EDD[reference:4].
Anatomy ultrasound — Typically performed at 18–22 weeks gestation[reference:5].

⚠️ Medical Disclaimer: This calculator provides an estimate based on Naegele's rule and ACOG guidelines. Only about 4-5% of babies are born on their exact due date[reference:6]. First-trimester ultrasound is the most accurate method for dating a pregnancy. Always consult your healthcare provider for personalized pregnancy care.

Understanding Your Baby's Due Date

What Is Naegele's Rule?

Naegele's rule is the standard method used to calculate the estimated date of delivery (EDD). The American College of Obstetricians and Gynecologists (ACOG) recommends calculating the EDD by adding 280 days (40 weeks) to the first day of the last menstrual period (LMP)[reference:7].

The rule can also be expressed as:

LMP + 7 days − 3 months — the classic formula[reference:8]
Assumes a 28-day menstrual cycle with ovulation on day 14[reference:9]
For cycles longer or shorter than 28 days, the due date should be adjusted[reference:10]

How Accurate Is the Due Date?

Only about 4-5% of babies are born on their exact due date[reference:11]. Most babies are born between 37 and 42 weeks of gestation. The most accurate method for dating a pregnancy is first-trimester ultrasound (before 14 weeks), which uses crown-rump length measurement and has a margin of error of ±5-7 days[reference:12].

Pregnancy Milestones

Weeks 1–12 (First Trimester): Organ formation, heartbeat detectable at 6-7 weeks, first-trimester screening at 11-14 weeks[reference:13].
Weeks 13–26 (Second Trimester): Quickening (first movements at 16-22 weeks), anatomy ultrasound at 18-22 weeks[reference:14].
Weeks 27–40 (Third Trimester): Rapid weight gain, viability at 24 weeks, full term at 37 weeks.

💡 Clinical Note: The American College of Radiology and ACOG recommend that first-trimester ultrasound using crown-rump length measurement should be performed if the patient presents early enough (before 14 weeks) to confirm or adjust the EDD based on LMP[reference:15].

References & Further Reading

American College of Obstetricians and Gynecologists. (2023). Methods for Estimating the Due Date. Committee Opinion No. 700.
Baskett, T.F. & Nagele, F. (2000). Naegele's rule: a reappraisal. British Journal of Obstetrics and Gynaecology, 107(11), 1433-1435.
American College of Radiology. (2021). ACR Practice Parameter for the Performance of Obstetric Ultrasound.

Frequently Asked Questions

Naegele's rule is the standard method recommended by ACOG for calculating the estimated due date (EDD). It adds 280 days (40 weeks) to the first day of the last menstrual period (LMP)[reference:16]. The rule assumes a 28-day cycle with ovulation on day 14[reference:17].

Due date calculators provide estimates. Only about 4-5% of babies are born on their exact due date. Most babies are born between 37 and 42 weeks. First-trimester ultrasound is the most accurate method for dating a pregnancy, with a margin of error of ±5-7 days[reference:18].

A pregnancy milestone timeline shows key dates and developmental milestones throughout your pregnancy. It includes the start of each trimester, important screening windows, and fetal development milestones like when the baby's heartbeat can be heard, when movement is typically felt, and when the baby reaches viability.

First-trimester screening for chromosomal abnormalities is typically performed between 11 and 14 weeks of gestation. This includes an ultrasound (nuchal translucency) and a blood test[reference:19].

The anatomy ultrasound is typically performed between 18 and 22 weeks of gestation. This detailed ultrasound examines the baby's anatomy, checks for structural abnormalities, and can determine the baby's sex[reference:20].

Naegele's rule assumes a 28-day cycle. For women with longer or shorter cycles, ACOG recommends adjusting the due date by adding the difference between the actual cycle length and 28 days[reference:21]. For example, with a 35-day cycle, add 7 days to the due date.

Gestational age is calculated from the first day of the last menstrual period (LMP) and is the standard used in pregnancy dating. Fetal age (or conception age) is calculated from the date of conception and is about 2 weeks less than gestational age. ACOG uses gestational age for clinical care[reference:22].