Due Date Calculator
Calculate your estimated delivery date (EDD), current gestational age, trimester dates, and 40-week milestone calendar using LMP, ultrasound, conception date, or IVF transfer.
Due Date Calculator
Calculate your baby's estimated delivery date (EDD), current gestational age in weeks and days, trimester timeline, and developmental milestones based on LMP, ultrasound, conception date, or IVF transfer.
Adjusts Naegele's rule based on your cycle length (+280 days + cycle length - 28 days).
Saturday, April 24, 2027
Only ~4% of babies are born on their exact calculated due date. Deliveries between 37 and 42 weeks are clinically considered healthy full-term births.
Trimester Calendar & Developmental Highlights
First Trimester
Rapid organogenesis, neural tube closure, and primitive heartbeat development.
- Fertilization & Implantation
- Heartbeat detected (~6 weeks)
- Formation of limbs, eyes, fingers
Second Trimester
Rapid fetal skeletal growth, quickening movements, and mid-pregnancy anatomy survey.
- Mother feels flutter kicks (quickening)
- Mid-pregnancy anatomy scan (20 weeks)
- Viability milestone reached (24 weeks)
Third Trimester
Lung surfactant maturation, rapid brain expansion, and substantial weight gain.
- Eyes open & responsive to light
- Lung alveoli mature for breathing
- Early full term reached at 37 weeks
Key Pregnancy Milestone Schedule
Calculated calendar dates from baseline LMP through delivery:
First Day of LMP
Obstetric dating baseline marker from which the 280-day gestational clock begins.
Estimated Conception
Fertilization of mature ovum by spermatozoon in the fallopian tube, creating a zygote.
Embryonic Heartbeat Detectable
Rhythmic cardiac contractions visible via transvaginal ultrasound (100–160 bpm).
End of 1st Trimester
Critical organogenesis complete; placenta fully operational; baseline miscarriage risk drops significantly.
Mid-Pregnancy / Anatomy Scan
Comprehensive level II structural ultrasound examining fetal heart, brain, spine, kidneys, and fetal sex.
Fetal Viability Landmark
Lungs begin producing surfactant; modern neonatal intensive care (NICU) viability threshold reached.
End of 2nd Trimester
Fetus opens eyelids, establishes regular sleep-wake cycles, and practices rhythmic breathing reflexes.
Early Full Term
Baby is considered fully developed; unassisted extrauterine breathing and feeding are safe.
Estimated Due Date (EDD)
Official 40-week delivery milestone (280 days from LMP / 266 days post-conception).
Late Term Landmark
Post-due milestone where antenatal biophysical profiles and amniotic fluid monitoring are conducted.
Explore Complementary Pregnancy & Health Calculators:
Estimation of Due Date: Methods, Accuracy & Full-Term Windows
Medically reviewed clinical principles of gestational dating according to the American College of Obstetricians and Gynecologists (ACOG) and the Society for Maternal-Fetal Medicine (SMFM).
The 40-Week Gestational Clock & The 4% Rule
An Estimated Due Date (EDD) is a statistical benchmark representing the completion of 280 days (40 full weeks) from the first day of your last menstrual period. It does not represent an expiration date or a guaranteed delivery appointment:
Large-scale clinical registry studies consistently demonstrate that only approximately 4% of women spontaneously deliver on their exact calculated due date. Around 80% of babies arrive within a 2-week window (from 38 to 42 weeks).
Calendar months average 30.4 days. 40 weeks equals 280 days, which is approximately 9 calendar months plus 1 week. Because clinical dating starts at the beginning of the menstrual cycle before conception, the baby spends 38 weeks (266 days) developing inside the uterus.
Frequently Asked Questions (FAQs)
Answers to common obstetric questions regarding due dates, cycle variation, and delivery timing.
This Due Date Calculator is intended strictly for educational and informational purposes based on standard obstetric formulas endorsed by the American College of Obstetricians and Gynecologists (ACOG). Estimated dates are statistical averages and do not represent a diagnosis or guaranteed delivery time. Always consult with a licensed obstetrician-gynecologist (OB-GYN), certified nurse-midwife, or healthcare professional for individualized prenatal care and clinical biometric ultrasound evaluation.
Understanding Due Date Calculator & Formula
The Due Date Calculator on CalculatorScale.com is engineered to deliver instant, mathematically verified calculations conforming strictly to standard institutional equations. Whether planning long-term investments, managing household budgets, tracking clinical fitness targets, analyzing academic genetics, calculating veterinary dosages, or converting dimensional units, every calculation updates dynamically in real time without lag.
Every formula used in this tool adheres to certified international standards, including World Health Organization biometric metrics, veterinary clinical guidelines, NIST physical conversion constants, and standard biological equations. Results are computed entirely client-side inside your browser with complete data privacy, ensuring your sensitive numbers and statistics never leave your device.
Our calculators are 100% free with no registration, subscriptions, or paywalls required. You can toggle between imperial and metric units, customize input parameters, export calculation summaries, or embed this calculator directly into your own website or blog.
How to Use the Due Date Calculator
- 1 Select your calculation method: Last Menstrual Period (LMP), Ultrasound Date, Conception Date, or IVF Transfer.
- 2 Enter the required dates and parameters (e.g., average cycle length, ultrasound scan gestational age, or IVF embryo type).
- 3 Click "Calculate Due Date" to generate your estimated delivery date, current gestational age in weeks/days, and full trimester schedule.
- 4 Explore key obstetric milestones from implantation through full term delivery (weeks 37–42).
Due Date Calculator — Frequently Asked Questions
Q1 How accurate is an estimated due date? ▾
Only approximately 4% of babies are born on their exact calculated due date. However, about 80% deliver within 2 weeks of their due date (between 38 and 42 weeks), which is clinically considered normal full term.
Q2 What is Naegele’s Rule? ▾
Naegele’s rule is a standard clinical formula that calculates your due date by adding 280 days (40 weeks) to the first day of your last menstrual period, adjusted for variations in your typical menstrual cycle length.
Q3 Why does ultrasound dating sometimes differ from LMP dating? ▾
LMP dating assumes standard 14-day ovulation in a 28-day cycle. An early first-trimester ultrasound directly measures the embryo’s Crown-Rump Length (CRL), which is accurate to within ±3 to 5 days and is considered the gold standard for clinical pregnancy dating.
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