Pregnancy Calculator & Tracker
Calculate your estimated due date (EDD), gestational age in weeks and days, conception window, and trimester milestones. Works for LMP, known conception, ultrasound scan dating, or IVF embryo transfers.
Gestational counting begins here.
Estimated fertilisation date.
Organogenesis complete; miscarriage risk drops sharply.
Survival odds begin rising significantly.
Final stretch of pregnancy begins.
Baby fully formed and ready for the world.
Your target delivery date.
Keep timing. Need at least 3 contractions to calculate frequency.
How Gestational Age & Due Dates Are Calculated
A pregnancy calculator estimates key milestones based on standard clinical metrics. Understanding gestational age (how far along you are) and your due date helps organize prenatal visits, schedule testing, and chart fetal development. Interestingly, only about 5% of babies are born precisely on their estimated due date—most are delivered within two weeks before or after.
LMP vs. Conception Dating vs. IVF Transfer
The **Last Menstrual Period (LMP)** method is the medical standard. It assumes a 28-day menstrual cycle and places ovulation on day 14. This means your calculated gestational age is actually two weeks older than the biological age of the embryo (conception age).
For pregnancies achieved through **In Vitro Fertilization (IVF)**, due dates are significantly more precise (±1-2 days). The calculation adjusts for the exact age of the embryo (typically Day 3 or Day 5 blastocyst) on the day of transfer to pinpoint milestones.
The Three Trimesters of Pregnancy
Critical organogenesis phase. All major organ systems form. Symptoms include nausea (morning sickness), profound fatigue, and breast changes. Miscarriage risk drops dramatically after week 12.
Often called the "golden period" as morning sickness subsides and energy returns. The baby grows rapidly, and quickening (first kicks) is typically felt around week 20.
Focuses on rapid fetal weight accumulation and lung maturity. The mother experiences heavier physical discomforts, Braxton Hicks contractions, and pressure as the baby drops in preparation for labor.
Safe Prenatal Practices
Prioritizing health and safety indices protects both mother and developing fetus during this gestational journey:
Avoid raw meat, fish (sushi), unpasteurized dairy, soft cheeses, and deli meats to prevent listeriosis. Limit caffeine consumption to under 200 mg per day.
Engage in moderate-intensity activities like swimming, walking, and prenatal yoga. Avoid contact sports, exercises with falling risks, or supine layouts after 20 weeks.
Contact your clinical provider immediately if you experience heavy bleeding, leaking fluid, severe abdominal pain, persistent headaches, or sudden vision changes.
Usually scheduled between weeks 8 and 10 of pregnancy. Start taking a daily prenatal vitamin containing folic acid as soon as you confirm a positive result.
Related Health & Fitness Tools
For comprehensive wellness tracking throughout your pregnancy journey, check out our other free calculations:
Frequently Asked Questions
Scientific answers to common questions about gestation, due dates, trimesters, and labor.
Q.How is the due date calculated?
The due date is calculated using Naegele's Rule: Due Date = First day of Last Menstrual Period (LMP) + 280 days (40 weeks). This assumes a 28-day cycle with ovulation on day 14. For longer or shorter cycles, adjust accordingly. Alternative methods include using the conception date (EDD = conception + 266 days) or ultrasound dating, which is most accurate (±3-5 days).
Q.How accurate are pregnancy due date calculators?
Pregnancy calculators are estimates: LMP method is accurate to within ±1-2 weeks, conception date to within ±1 week, and ultrasound dating to within ±3-5 days. IVF pregnancies can be calculated to within ±1-2 days. Only about 5% of babies are born on their exact due date - most arrive within 2 weeks before or after. Full term is 37-42 weeks.
Q.How many weeks pregnant am I?
To calculate how many weeks pregnant you are: 1) Find the first day of your last menstrual period (LMP), 2) Count the weeks from LMP to today. For example, if your LMP was 8 weeks ago, you're 8 weeks pregnant. Pregnancy is counted from LMP (not conception) because it's a more definite date. Use our calculator above for your exact gestational age in weeks and days.
Q.When is the first trimester?
The first trimester spans weeks 1-13 of pregnancy (months 1-3), counted from the first day of your last menstrual period. It begins at conception and ends around week 13. This trimester is critical for baby's development (all major organs form) and has the highest risk of miscarriage. Most women don't show much physically, but experience symptoms like morning sickness, fatigue, and breast tenderness.
Q.When is the second trimester?
The second trimester spans weeks 14-27 (months 4-6). It's often called the 'golden period' because most women feel their best - morning sickness usually ends, energy returns, and the baby bump becomes visible. You'll feel first movements (quickening) around week 20. The anatomy scan ultrasound happens at 18-22 weeks, where you can often learn the baby's sex.
Q.When is the third trimester?
The third trimester spans weeks 28 to birth (months 7-9). During this final stage, the baby rapidly gains weight, organs mature (especially lungs), and brain development accelerates. You'll experience more discomfort: back pain, heartburn, shortness of breath, frequent urination, and difficulty sleeping. Weekly doctor visits begin at week 36. The baby is considered full-term at 37 weeks.
Q.How is IVF due date calculated?
For IVF pregnancies, the due date is calculated from the embryo transfer date: 1) Day 3 embryo transfer: Due date is transfer date + 263 days (38 weeks + 5 days from transfer). 2) Day 5/6 blastocyst transfer: Due date is transfer date + 261 days. 3) Known conception date (egg retrieval): Due date is conception + 266 days. IVF due dates are very accurate (±1-2 days) because the exact age of the embryo is known.
Q.What is the most accurate way to calculate due date?
The most accurate methods, in order: 1) IVF transfer date (±1-2 days, as embryo age is exact), 2) First trimester ultrasound (±3-5 days, most accurate ultrasound), 3) Known conception date (±1 week), 4) LMP with regular cycles (±1-2 weeks). Second/third trimester ultrasounds are less accurate. Early ultrasounds (before 14 weeks) are most reliable for dating the pregnancy.
Q.What percentage of babies are born on their due date?
Only about 5% of babies are born on their exact estimated due date. Approximately 80% are born within 2 weeks of the due date (between 38-42 weeks). About 10% are born premature (before 37 weeks). The 'due date' is really just an estimate - full term is anywhere from 37-42 weeks, so try not to focus on the exact day.
Q.What is the difference between gestational age and fetal age?
Gestational age is measured from the first day of the last menstrual period (LMP), which is typically 2 weeks before conception. Fetal age (or conception age) is measured from actual conception. So at 8 weeks gestational age, the fetus is actually 6 weeks old. Doctors use gestational age because the LMP is a more definite date than conception. Always clarify which is being referenced when discussing pregnancy.
Q.When should I see a doctor for pregnancy confirmation?
Schedule your first prenatal appointment as soon as you suspect pregnancy: 1) Home pregnancy test positive (around 4 weeks), 2) First prenatal visit typically at 8-10 weeks, 3) Earlier if you have risk factors (age 35+, medical conditions, previous complications), 4) Earlier if you have concerning symptoms (bleeding, severe pain). Start taking prenatal vitamins with folic acid as soon as you suspect pregnancy.
Q.How is twin pregnancy different from singleton?
Twin pregnancies differ in several ways: 1) Due date is typically earlier (37 weeks average vs 40), 2) More weight gain needed (37-54 lbs vs 25-35 lbs), 3) More frequent prenatal visits, 4) Higher risk of complications (preterm labor, gestational diabetes, preeclampsia), 5) More intense symptoms (morning sickness, fatigue), 6) C-section more likely, 7) Earlier detection of multiples (first ultrasound at 6-8 weeks).
How Pregnancy Calculator - Due Date & Week-by-Week Tracker Works
Our high-performance online utility runs entirely client-side, processing your requests securely and instantly inside your web browser. For related features, you can also use our Gestational Age and Tools tools.
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Frequently Asked Questions
Does this include IVF and twin pregnancy calculations?
Yes. Calculate due date with LMP, ultrasound, and IVF transfer. Includes twin pregnancy tracking offline.