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Calculate your pregnancy due date and track your journey through each trimester
Normal range: 21-35 days (default is 28 days)
Note: This calculator provides an estimate. Only 4-5% of babies arrive exactly on their due date. Most deliver within 2 weeks before or after. Your healthcare provider may adjust your due date based on ultrasound measurements.
Enter your date above to calculate your due date
Pregnancy due dates are calculated using Naegele's Rule, a formula developed by German obstetrician Franz Karl Naegele in the early 1800s. This rule adds 280 days (40 weeks) to the first day of your last menstrual period (LMP), assuming a regular 28-day menstrual cycle with ovulation occurring on day 14. The calculation is based on the average human gestation period of 280 days from LMP or 266 days from conception (ovulation date).
The calculation assumes you know the exact date of your last period and have a regular cycle. For women with irregular cycles, longer or shorter than 28 days, or those who don't remember their LMP, the due date calculation becomes less accurate. In these cases, healthcare providers rely on early ultrasound measurements to establish gestational age and due dates. First-trimester ultrasounds (performed between 8-13 weeks) measuring crown-rump length (CRL) provide the most accurate dating, typically within 3-5 days of the actual due date.
It's crucial to understand that your due date is an estimate, not a deadline. Only about 4-5% of babies arrive exactly on their due date. The majority of babies (about 80%) are born within two weeks before or after the estimated due date. This natural variation occurs because every pregnancy is unique, influenced by factors including maternal age, first versus subsequent pregnancy, genetics, ethnicity, and individual fetal development patterns. Think of your due date as the center of a target window rather than a specific date you must hit.
Healthcare providers now use more specific terminology than simply "due date." The term "estimated due date" (EDD) or "expected date of delivery" acknowledges the inherent uncertainty. Additionally, modern obstetrics recognizes that full-term pregnancy actually spans a range: early term (37-38 weeks), full term (39-40 weeks), late term (41 weeks), and post-term (42+ weeks). Research shows that babies born at 39-40 weeks have the best outcomes with fully developed organs, particularly lungs and brain, which is why elective inductions and cesarean sections are typically scheduled no earlier than 39 weeks without medical indication.
Pregnancy is divided into three distinct trimesters, each approximately 13-14 weeks long, characterized by specific developmental milestones for the baby and physical changes for the mother. Understanding what to expect during each trimester helps you prepare mentally, physically, and emotionally for the journey ahead.
The first trimester encompasses the most dramatic changes in fetal development. After fertilization in week 2 (pregnancy weeks are counted from your LMP, so conception typically occurs in week 2-3), the fertilized egg travels down the fallopian tube and implants in the uterine lining around days 6-12. By week 4, the embryo is smaller than a grain of rice but developing rapidly. The neural tube, which becomes the brain and spinal cord, forms and closes. The heart begins beating around day 21-22, often visible on ultrasound by week 6.
By week 8, all major organs have begun forming—heart, lungs, kidneys, liver, and brain. The embryo officially becomes a fetus at the end of week 10. Facial features develop, arms and legs form with fingers and toes, bones begin hardening, and external genitalia start developing (though not yet distinguishable on ultrasound). By the end of week 13, your baby is about 3 inches long and weighs approximately 1 ounce, roughly the size of a peach. All major organs and body systems are present, though they'll continue maturing throughout pregnancy.
The first trimester brings significant hormonal changes that cause various symptoms. Morning sickness (nausea and vomiting) affects 70-80% of pregnant women, typically beginning around week 6 and peaking around weeks 9-10 before improving by week 14. Despite its name, morning sickness can occur at any time of day. Extreme fatigue is nearly universal, caused by rising progesterone levels and your body's increased metabolic demands.
Breast tenderness and enlargement begin within weeks of conception due to increased estrogen and progesterone. Frequent urination starts early as your expanding uterus presses on your bladder and blood volume increases by 50% over pregnancy. Food aversions and heightened sense of smell are common, while some women experience strong food cravings. Mood swings result from hormonal fluctuations and emotional adjustment to pregnancy. Weight gain in the first trimester is typically minimal (0-5 pounds) or you may even lose weight if experiencing significant morning sickness.
The second trimester is marked by rapid growth and refinement of existing organ systems. By week 16, your baby is about 5 inches long and weighs 4 ounces. Facial features become more defined, and the baby begins making facial expressions, sucking thumb, and yawning. The skeleton continues hardening from soft cartilage to bone, though it remains flexible. Fine hair (lanugo) covers the body, and eyebrows and eyelashes appear.
Around week 18-20, you'll likely feel first movements (quickening)—first-time mothers typically notice this slightly later than those with previous pregnancies. At the 20-week anatomy ultrasound, your baby is about 10 inches long and weighs 10 ounces. All major organs and body structures are examined in detail. By the end of the second trimester, your baby is about 14 inches long and weighs 2 pounds. Brain development accelerates dramatically, with billions of neurons forming.
Many women call the second trimester the "honeymoon period" of pregnancy. Morning sickness typically resolves by week 14-16, and energy levels rebound significantly. Your baby bump becomes visible, usually between weeks 16-20 for first pregnancies and earlier for subsequent pregnancies. Weight gain accelerates to approximately 1 pound per week. You'll feel baby movements, which is exciting and reassuring. Back pain may develop as your center of gravity shifts.
The third trimester focuses on growth and maturation, particularly lung and brain development. At week 28, your baby is about 15 inches long and weighs 2.5 pounds. Eyes can open and close, and the baby responds to light with movement. From weeks 32-36, your baby gains about half a pound weekly. Fat deposits accumulate under the skin, giving the baby a plumper appearance and helping with temperature regulation after birth.
At 40 weeks (full term), the average baby is 19-21 inches long and weighs 6.5-8.5 pounds, though variation is normal. All organs are fully functional, the immune system has received antibodies from you (providing protection for the first few months), and the baby is ready for birth.
Physical discomfort typically increases as your body prepares for delivery. Your uterus expands causing shortness of breath. Heartburn and indigestion worsen as your stomach is compressed. Frequent urination returns with a vengeance as the baby's head drops into your pelvis. Sleep becomes challenging due to discomfort and difficulty finding comfortable positions. Swelling in feet, ankles, and hands is common. Back pain and pelvic pressure intensify as your baby grows and drops lower.
While pregnancy is a natural process, certain symptoms require immediate medical attention. Understanding warning signs helps you distinguish between normal pregnancy discomforts and potentially serious complications. Always err on the side of caution—your healthcare provider would rather evaluate a false alarm than have you delay seeking help for a genuine emergency.
Trust your instincts—if something feels wrong, call your provider. They have experience distinguishing between normal pregnancy variations and concerning symptoms. Most prenatal offices have 24/7 nurse lines, and they expect to receive calls about symptoms and concerns.
Due dates are calculated using Naegele's Rule: add 280 days (40 weeks) to the first day of your last menstrual period (LMP). This assumes a 28-day cycle with ovulation on day 14. For irregular cycles, healthcare providers use early ultrasound measurements (typically 8-13 weeks) for more accurate dating. Ultrasound measurements of crown-rump length provide the most precise estimates. Only 4-5% of babies arrive exactly on their due date—most deliver within 2 weeks before or after. See our calculation methodology section for details.
Due date calculations provide estimates with natural variation. LMP-based calculations are accurate within 1-2 weeks for women with regular 28-day cycles. Early ultrasound (before 13 weeks) is most accurate, typically within 3-5 days. Later ultrasounds become less accurate for dating. Only 4-5% of babies arrive on the exact due date, with 80% delivering within 2 weeks either side. Factors affecting timing include first pregnancy (often later), previous pregnancy history, maternal age, and individual variation. Your due date is better viewed as a "due month" or target window.
If you don't remember your LMP or have irregular cycles, your healthcare provider will use early ultrasound for dating. First-trimester ultrasounds (8-13 weeks) measuring crown-rump length provide the most accurate estimates. Dating ultrasounds should be performed as early as possible for best accuracy. If you know conception date (from fertility treatments or single intercourse), add 266 days (38 weeks). Home pregnancy test dates can help narrow the timeframe. Your provider may also consider cycle length patterns, previous pregnancy spacing, and physical examination findings.
Due dates typically don't change after being established by early ultrasound. If initially calculated from LMP but an early ultrasound (before 13 weeks) differs by more than 5-7 days, providers usually adjust to the ultrasound date as it's more accurate. After the first trimester, due dates shouldn't be changed based on ultrasound measurements since growth rates vary significantly between babies. Later ultrasounds estimate fetal weight and development but aren't reliable for dating. Once your due date is set by early ultrasound, it generally remains fixed throughout pregnancy.
Full term is now classified into categories rather than a single definition. Early term is 37-38 weeks, full term is 39-40 weeks, late term is 41 weeks, and post-term is 42+ weeks. The American College of Obstetricians and Gynecologists emphasizes that babies born at 39-40 weeks have the best outcomes with fully mature lungs, brain development, and lower complication risks. Elective deliveries shouldn't occur before 39 weeks without medical indication. Most providers induce labor between 41-42 weeks to prevent post-term complications.
Normal pregnancy length is 37-42 weeks from the first day of your last menstrual period. The average is 40 weeks (280 days), but this is just an average. First-time mothers often deliver slightly later (40 weeks 5 days average) compared to subsequent pregnancies (40 weeks 3 days). Only 4-5% deliver exactly on their due date. About 80% deliver within 2 weeks either side. Pregnancies before 37 weeks are considered preterm, while those continuing past 42 weeks are post-term and typically require medical intervention.
Pregnancy divides into three trimesters. First trimester (weeks 1-13) involves fertilization, implantation, and major organ formation. Common symptoms include morning sickness, fatigue, breast tenderness, and frequent urination. Second trimester (weeks 14-27) brings energy return, baby movements (quickening), and visible bump growth. Third trimester (weeks 28-40+) features rapid fetal growth, preparation for birth, and increased discomfort including back pain, shortness of breath, and frequent urination. Each trimester brings distinct developmental milestones for baby and physical changes for mother.
First-time mothers typically feel baby movements (quickening) between 18-25 weeks, often around 20 weeks. Women who've been pregnant before may notice movements earlier, sometimes as early as 16 weeks, because they recognize the sensation. Initial movements feel like flutters, gas bubbles, or gentle tapping. By 24-28 weeks, movements become stronger and more distinct, including kicks, rolls, and hiccups. Movement patterns become regular in the third trimester. Decreased movement after 28 weeks should be reported to your healthcare provider immediately.
Standard prenatal visit schedules are: monthly visits until 28 weeks, bi-weekly visits from 28-36 weeks, and weekly visits from 36 weeks until delivery. High-risk pregnancies require more frequent monitoring. First prenatal visit typically occurs at 8-12 weeks for confirmation, dating ultrasound, blood work, and health history. Key appointments include nuchal translucency screening (11-14 weeks), anatomy ultrasound (18-22 weeks), glucose screening (24-28 weeks), and Group B strep testing (35-37 weeks). Additional visits may be needed for specific concerns or complications.
Standard pregnancy tests include: First trimester blood work (blood type, Rh factor, complete blood count, infectious disease screening, genetic carrier screening). Nuchal translucency ultrasound (11-14 weeks) screens for chromosomal abnormalities. Anatomy ultrasound (18-22 weeks) examines fetal development and placenta location. Glucose tolerance test (24-28 weeks) screens for gestational diabetes. Group B streptococcus culture (35-37 weeks) checks for bacterial colonization. Optional tests include cell-free DNA screening, amniocentesis, or chorionic villus sampling for genetic conditions. Your provider will discuss appropriate testing based on your situation.
Exercise is generally safe and beneficial during uncomplicated pregnancies. Benefits include better weight management, reduced back pain, improved mood, easier labor, and faster postpartum recovery. Safe activities include walking, swimming, prenatal yoga, stationary cycling, and modified strength training. Aim for 150 minutes of moderate-intensity exercise weekly. Avoid contact sports, activities with fall risk, hot yoga, scuba diving, and exercises lying flat on your back after 20 weeks. Stay hydrated, avoid overheating, and stop if experiencing dizziness, chest pain, vaginal bleeding, or contractions. Always consult your provider before starting exercise.
Avoid: raw or undercooked meat, poultry, eggs, and seafood (risk of bacterial contamination); high-mercury fish like swordfish, king mackerel, tilefish (limit tuna to 6oz weekly); unpasteurized dairy and soft cheeses (listeria risk); deli meats and hot dogs unless heated steaming (listeria risk); raw sprouts, unwashed produce; alcohol (no safe amount); excessive caffeine (limit to 200mg daily). Limit processed foods high in additives. Most foods are safe when properly cooked and handled. Focus on variety including fruits, vegetables, whole grains, lean proteins, and adequate hydration.
Recommended weight gain depends on pre-pregnancy BMI. Underweight (BMI <18.5): gain 28-40 pounds. Normal weight (BMI 18.5-24.9): gain 25-35 pounds. Overweight (BMI 25-29.9): gain 15-25 pounds. Obese (BMI ≥30): gain 11-20 pounds. For twins, recommendations increase by 50-100%. Most gain occurs in second and third trimesters (roughly 1 pound weekly after first trimester). Inadequate gain increases preterm birth risk, while excessive gain raises risks of gestational diabetes, hypertension, cesarean delivery, and postpartum weight retention. Regular monitoring helps maintain healthy gain trajectory.
Braxton Hicks are "practice contractions" that prepare your uterus for labor without causing cervical changes. They typically begin in the second or third trimester, becoming more frequent and intense as pregnancy progresses. Characteristics include irregular timing, variable intensity, usually painless (though may be uncomfortable), stop with position changes or hydration, felt primarily in the front of the abdomen. True labor contractions are regular, increasing in intensity and frequency, continue despite movement, felt in back radiating forward, and cause cervical dilation. If unsure, contact your provider, especially before 37 weeks.
For first-time mothers, go to the hospital when contractions are 5 minutes apart, lasting 1 minute each, for 1 hour (5-1-1 rule). For subsequent pregnancies, go when contractions are 5-7 minutes apart. Also go immediately if: water breaks (especially if fluid is green/brown or you're not in labor), severe bleeding, decreased fetal movement, severe headache with vision changes, constant severe abdominal pain, or intuition that something is wrong. Before 37 weeks, contact your provider about any regular contractions. First-time labor averages 12-18 hours, so you typically have time. Follow your provider's specific instructions.
This calculator provides estimates for educational purposes only and should not replace professional medical care. Due dates are estimates, and only 4-5% of babies arrive exactly on their calculated due date. Your healthcare provider will use ultrasound measurements and physical examinations to establish and potentially adjust your due date. Every pregnancy is unique, and your provider should be consulted for personalized prenatal care, especially if you have high-risk factors, medical conditions, irregular cycles, or fertility treatment. Seek immediate medical attention for vaginal bleeding, severe abdominal pain, decreased fetal movement after 28 weeks, or any concerning symptoms during pregnancy.