Pregnancy Due Date Calculator
Estimate your baby's due date, current pregnancy week, trimester, and key milestones. Calculate by last menstrual period (LMP), conception date, ultrasound, or IVF transfer date. Works worldwide.
Find out when your baby is due, how far along you are, and which trimester you're in. Choose the calculation method that fits your situation.
| Milestone | Week | Estimated Date | Status |
|---|
* Estimates are for informational purposes only. Only about 4 in 100 babies are born on their exact due date. Always confirm dates and pregnancy progress with your healthcare provider, midwife, or OB-GYN.
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What Is a Pregnancy Due Date Calculator?
A pregnancy due date calculator is a free online tool that estimates the date your baby is most likely to be born — also known as the Estimated Due Date (EDD) or Estimated Date of Confinement (EDC). Our calculator uses the same proven methods that doctors, midwives, and OB-GYNs use worldwide, including Naegele's Rule for last menstrual period (LMP) calculations and standard adjustments for IVF transfers and ultrasound measurements.
Whether you've just found out you're pregnant, you're trying to plan your maternity leave, or you simply want to know how far along you are, this calculator gives you accurate results in seconds — no sign-up, no app download, no personal information required.
How to Use This Pregnancy Calculator
Using the calculator is simple. Choose the method that matches your situation:
- Last Menstrual Period (LMP) — the most common method. Enter the first day of your last period. If your cycle isn't 28 days, adjust the cycle length field for a more accurate result.
- Conception Date — if you know the exact date you conceived (or ovulated), use this option for a precise estimate.
- Ultrasound Date — if your doctor measured your baby and gave you a gestational age, enter the ultrasound date and how many weeks and days along you were.
- IVF Transfer Date — if you conceived through IVF, choose Day 3 or Day 5 transfer based on your procedure. This is the most accurate method available.
Click Calculate Due Date and you'll instantly see your estimated due date, how many weeks pregnant you are, your current trimester, days remaining, and key milestones throughout your pregnancy.
How Is the Due Date Calculated?
The standard medical formula for calculating a pregnancy due date is called Naegele's Rule, developed by German obstetrician Franz Karl Naegele in the early 1800s. It works like this:
Or equivalently:
EDD = LMP + 1 year − 3 months + 7 days
For cycles longer or shorter than 28 days:
EDD = LMP + 280 days + (Cycle Length − 28)
A full-term pregnancy is counted as 40 weeks from the first day of your last period, even though actual fertilization usually happens about 2 weeks after that. This is why your "pregnancy weeks" already start at 2 weeks before conception actually occurs — it's a convention used by every doctor worldwide.
The Three Trimesters Explained
Pregnancy is divided into three trimesters, each with distinct developmental milestones:
First Trimester (Weeks 1–13): Major organs form. You may experience morning sickness, fatigue, and breast tenderness. Most miscarriages occur in this window, so it's important to attend early prenatal appointments. By week 12, your baby is roughly the size of a lime.
Second Trimester (Weeks 14–27): Often called the "honeymoon" trimester. Morning sickness usually fades, energy returns, and you'll likely feel the baby's first movements (called "quickening") around weeks 18–22. The anatomy scan happens around week 20, where you can often learn the baby's sex.
Third Trimester (Weeks 28–40): Baby gains the most weight. You'll have more frequent prenatal visits, prepare your hospital bag, and finalize your birth plan. Babies born after week 37 are considered full-term.
Key Pregnancy Milestones
| Week | Milestone | What Happens |
|---|---|---|
| Week 6 | First Prenatal Visit | Heartbeat often detected on ultrasound |
| Week 12 | End of 1st Trimester | Miscarriage risk drops sharply |
| Week 13 | NIPT Genetic Testing | Non-invasive screening available |
| Week 20 | Anatomy Scan | Detailed ultrasound; often reveals sex |
| Week 24 | Viability Milestone | Baby could survive outside womb (with NICU care) |
| Week 28 | Start of 3rd Trimester | Glucose test for gestational diabetes |
| Week 37 | Full Term | Baby is ready to be born safely |
| Week 40 | Estimated Due Date | Only ~4% of babies are born exactly on this date |
How Accurate Is a Due Date Calculator?
Pregnancy due dates are estimates, not guarantees. Research published in medical journals shows that:
- Only about 4 in 100 babies are born on their exact due date.
- About 80% of babies are born within 2 weeks before or after the due date.
- Normal pregnancies last anywhere from 37 to 42 weeks.
- First-time mothers tend to deliver slightly later than the calculated date.
- Early ultrasounds (before week 13) are the most accurate way to confirm gestational age.
If your cycles are irregular, your LMP-based due date may be less accurate. In that case, your doctor will likely adjust your due date based on early ultrasound measurements.
LMP vs. Conception Date vs. Ultrasound: Which Is Most Accurate?
LMP (Last Menstrual Period): Most commonly used because most women know when their last period started. Works best for regular 28-day cycles.
Conception Date: More accurate than LMP, but most women don't know the exact day of conception. Best suited for tracked ovulation or known intercourse dates.
Ultrasound: The gold standard, especially when done between weeks 8–13. An early ultrasound can predict the due date within ±5 days.
IVF Transfer Date: The most precise method possible because the exact embryo age is known. Day-3 and Day-5 transfers have slightly different calculation rules, which this calculator handles automatically.
Pregnancy Tips for Each Trimester
- Take a daily prenatal vitamin with at least 400 mcg of folic acid, ideally starting before conception.
- Stay hydrated — aim for 8–12 cups of water daily, more in hot climates.
- Eat for two, but smartly. You only need an extra ~340 calories in the 2nd trimester and ~450 calories in the 3rd — not double.
- Stay active with low-impact exercise like walking, swimming, or prenatal yoga, unless your doctor advises against it.
- Avoid alcohol, smoking, raw fish, unpasteurized dairy, and high-mercury fish throughout pregnancy.
- Attend all prenatal appointments — early and consistent care is the single biggest factor in healthy outcomes.