Calculate Your Due Date
Choose a method and enter the relevant date to find your EDD
Trimester Breakdown
Key Pregnancy Dates
What Is a Pregnancy Due Date?
Understanding EDD and how pregnancy duration is measured
A pregnancy due date — officially called the Estimated Due Date (EDD) — is the date on which a pregnant person is expected to give birth. It is an estimate, not a guarantee: only about 4–5% of babies are born exactly on their due date.
A full-term pregnancy lasts approximately 40 weeks (280 days) measured from the first day of the Last Menstrual Period (LMP). This is the internationally recognised standard, known as Naegele's Rule, developed by German obstetrician Franz Karl Naegele in the early 19th century.
About 80% of births occur between 37 and 42 weeks of gestation. Births before 37 weeks are premature (preterm), while births after 42 weeks are post-term. Your healthcare provider uses the EDD as the central reference point for scheduling scans, tests and checkups throughout your pregnancy.
How Is the Due Date Calculated?
The methods and formulas behind pregnancy due date estimation
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1
Naegele's Rule (LMP Method)
Take the first day of your Last Menstrual Period → Add 1 year → Subtract 3 months → Add 7 days. This equals +280 days from LMP. For cycles other than 28 days, the formula adjusts: EDD = LMP + 280 + (cycleLength − 28).
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2
Cycle Length Adjustment
If your cycle is longer than 28 days, ovulation happens later and your EDD shifts forward. Shorter cycles pull it earlier. A 35-day cycle adds 7 days to the standard EDD; a 21-day cycle subtracts 7 days.
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3
Conception Date Method
If you know exactly when conception occurred, add 266 days (38 weeks) to that date. This is more accurate than LMP-based calculation because it eliminates the assumption about when ovulation occurred.
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4
IVF Transfer Date Method
For a Day 3 embryo transfer: add 263 days to the transfer date. For a Day 5 blastocyst transfer: add 261 days. Since the embryo's exact age is known, IVF due dates are among the most precise.
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5
Current Gestational Age
Gestational age = (Today − LMP) ÷ 7 days. This determines which trimester you're in, when key scans are due and which developmental milestones apply to your baby right now.
EDD = LMP + 280 + (cycleLength − 28) days
Weeks Pregnant = (Today − LMP) ÷ 7
Days Remaining = EDD − TodayBaby's Development Week by Week
Key milestones throughout all 40 weeks of pregnancy
🌱 Fertilisation & Implantation
The egg is fertilised by sperm, forming a zygote. It divides rapidly into a blastocyst and implants into the uterine wall. The placenta and amniotic sac begin forming. hCG hormone rises — this is what a pregnancy test detects.
💓 The Heart Begins Beating
The embryo is now about the size of a lentil. By week 6, the heart starts beating — around 100–160 beats per minute. The brain, spinal cord, and all major organs begin forming. Facial features start taking shape. Morning sickness often peaks in this period.
🤏 Embryo Becomes a Fetus
At week 10, the embryo is officially called a fetus. All major organs are present. Fingers and toes separate. The nuchal translucency (NT) scan happens around week 11–13 to screen for chromosomal conditions like Down's syndrome.
👶 The Golden Period
Most pregnancy symptoms ease. Baby's sex can be seen on the anatomy scan around week 18–20. You'll feel kicks ("quickening") from week 18–22. Baby can hear sounds from week 25. The anomaly (morphology) scan at week 20 checks all major structures.
🌟 Final Countdown
Baby gains most of its weight in this period — about 200g per week. Lungs mature, which is critical for survival outside the womb. Brain develops rapidly. Baby moves into a head-down position by week 36. From week 37 the baby is considered full-term and ready for birth.
Interesting Facts About Pregnancy
Surprising and fascinating facts about pregnancy and fetal development
Heart Starts at 22 Days
A baby's heart begins beating just 22 days after conception — often before the mother even knows she is pregnant. It beats at about 160 beats per minute in early pregnancy.
Brain Cells by the Billions
During pregnancy, the fetal brain generates 250,000 neurons every single minute. By birth, a baby has over 100 billion brain cells — more than at any other point in life.
Unique Fingerprints at 9 Weeks
A fetus develops unique fingerprints as early as week 9. These ridge patterns form due to random movements in the womb and are never duplicated by anyone else — ever.
Baby Swallows Amniotic Fluid
From about 12 weeks, the baby begins swallowing amniotic fluid. By the third trimester, it swallows up to 1 litre per day — practising drinking and preparing the digestive system.
Babies Dream in the Womb
From around week 23, babies enter REM sleep cycles. Research shows brain activity identical to dreaming adults, along with rapid eye movements — suggesting babies dream before they're even born.
Baby Can Smell & Taste
By the third trimester, babies can smell and taste what their mother eats through the amniotic fluid. Newborns have been shown to prefer flavours they experienced in the womb.
The Uterus Expands 500×
The uterus grows from the size of a small fist (about 60g) to over 1 kg during pregnancy — expanding its volume approximately 500 times. It returns to near-normal size within weeks of birth.
385,000 Babies Born Daily
Approximately 385,000 babies are born every single day globally — about 4.5 babies every second. That means while you read this sentence, roughly 5 new humans entered the world.
Frequently Asked Questions
Common questions about pregnancy due date calculation