Pregnancy Calculator — Due Date, Week & Trimester Tracker
Enter your last menstrual period, conception date, or IVF transfer date to find your estimated due date, current week, and trimester milestones.
Your Pregnancy Progress
Key Pregnancy Milestones
| Milestone | Estimated Date | Week |
|---|
| Trimester | Weeks | Key Developments |
|---|---|---|
| First Trimester | Week 1 – 12 | Organ formation, heartbeat begins, morning sickness common |
| Second Trimester | Week 13 – 26 | Baby movements felt, gender visible on ultrasound, energy returns |
| Third Trimester | Week 27 – 40 | Rapid growth, lungs mature, baby moves into birth position |
What Is a Pregnancy Due Date Calculator?
A pregnancy due date calculator is an online tool that estimates the date your baby is expected to be born. Also known as an Expected Date of Delivery (EDD) calculator, it uses the date of your last menstrual period (LMP), conception date, or IVF transfer date to project a 40-week gestational timeline. While only about 5% of babies are born on their exact due date, knowing your EDD helps you and your healthcare provider plan prenatal care, schedule important tests, and prepare for delivery.
How Does the Pregnancy Calculator Work?
Our free pregnancy calculator supports three calculation methods:
1. Last Menstrual Period (LMP) Method
This is the most commonly used method, based on Naegele's Rule. It calculates your due date by adding 280 days (40 weeks) to the first day of your last menstrual period, adjusted for your average cycle length. If your cycle is longer or shorter than the standard 28 days, the calculator adjusts the estimated ovulation date accordingly.
Formula: Due Date = LMP + 280 days + (Cycle Length − 28) days
2. Conception Date Method
If you know the approximate date of conception (ovulation), the calculator adds 266 days (38 weeks) to that date. This method is useful for women who track ovulation through basal body temperature, ovulation predictor kits, or fertility apps. For more on tracking your fertile window, see our Ovulation Calculator.
3. IVF Transfer Date Method
For women who conceived through in vitro fertilization, the calculator uses the embryo transfer date and adjusts based on whether a Day 3 or Day 5 (blastocyst) embryo was transferred. This provides the most precise EDD for IVF pregnancies.
- Day 5 transfer: Due Date = Transfer Date + 261 days
- Day 3 transfer: Due Date = Transfer Date + 263 days
Understanding Pregnancy Weeks and Trimesters
A full-term pregnancy lasts approximately 40 weeks (280 days) from the first day of the last menstrual period. This timeline is divided into three trimesters, each with distinct developmental milestones:
First Trimester (Weeks 1–12)
- Weeks 1–4: Fertilization occurs, the embryo implants in the uterine wall, and early cell division begins.
- Weeks 5–8: The heart begins to beat, brain and spinal cord form, and tiny limb buds appear. Many women experience morning sickness during this period.
- Weeks 9–12: All major organs are formed. The embryo is now called a fetus. Fingers and toes develop, and the risk of miscarriage decreases significantly after week 12.
Second Trimester (Weeks 13–26)
- Weeks 13–16: The baby's sex may be visible on ultrasound. Facial features become more defined.
- Weeks 17–20: You may feel the first fetal movements (quickening). The anatomy scan ultrasound is typically performed around week 20.
- Weeks 21–26: The baby develops a sleep-wake cycle, hearing improves, and the lungs begin to produce surfactant. This is often called the most comfortable trimester.
Third Trimester (Weeks 27–40)
- Weeks 27–32: Rapid brain development and weight gain. The baby can open and close its eyes and respond to light.
- Weeks 33–36: The baby moves into a head-down position in preparation for birth. Lungs continue to mature.
- Weeks 37–40: The baby is considered full-term at 39 weeks. Final weight gain occurs, and the baby drops lower into the pelvis (lightening).
The American College of Obstetricians and Gynecologists (ACOG) provides detailed week-by-week fetal development information.
Important Prenatal Tests and Screenings
Throughout your pregnancy, several key tests and screenings help monitor your health and your baby's development:
- First prenatal visit (Week 8–10): Confirms pregnancy, estimates due date, blood tests, and medical history review.
- First trimester screening (Week 11–13): Nuchal translucency ultrasound and blood tests to assess risk of chromosomal abnormalities.
- Anatomy scan (Week 18–22): Detailed ultrasound to check baby's organs, growth, and placenta position.
- Glucose screening (Week 24–28): Tests for gestational diabetes.
- Group B Strep test (Week 35–37): Screens for bacteria that could affect the baby during delivery.
- Non-stress test (Week 36+): Monitors baby's heart rate and movement in high-risk pregnancies.
Nutrition During Pregnancy
Proper nutrition is critical for a healthy pregnancy. Key nutritional needs include:
- Folic acid (400–800 mcg/day): Essential for neural tube development, especially in the first trimester. Found in leafy greens, fortified cereals, and supplements.
- Iron (27 mg/day): Supports increased blood volume and prevents anemia. Sources include lean red meat, spinach, and lentils.
- Calcium (1,000 mg/day): Builds baby's bones and teeth. Found in dairy, fortified plant milks, and broccoli.
- Protein (1.1 g/kg/day): Supports fetal growth and placental development. Use our Protein Calculator to find your daily needs.
- DHA omega-3 (200–300 mg/day): Supports brain and eye development. Found in fatty fish, walnuts, and algae supplements.
- Calories: No extra calories needed in the first trimester; add ~340 kcal/day in the second and ~450 kcal/day in the third trimester.
Explore balanced meal ideas on our Healthy Recipes page and learn about traditional pregnancy nutrition on our Ayurveda & Wellness page.
Exercise During Pregnancy
The World Health Organization recommends at least 150 minutes of moderate-intensity aerobic activity per week during pregnancy. Safe exercises include:
- Walking and swimming
- Prenatal yoga and stretching (visit our Yoga section for gentle routines)
- Stationary cycling
- Low-impact aerobics
- Pelvic floor exercises (Kegels)
Avoid contact sports, activities with a high risk of falling, and exercises that involve lying flat on your back after the first trimester. Always consult your healthcare provider before starting or continuing an exercise program during pregnancy.
Common Pregnancy Symptoms by Trimester
First Trimester
Morning sickness, fatigue, breast tenderness, frequent urination, food aversions, and mood swings. Many of these symptoms ease by week 12–14. Explore natural relief options on our Home Remedies page.
Second Trimester
Increased energy, visible baby bump, back pain, leg cramps, nasal congestion, and skin changes (linea nigra, stretch marks). Most women feel their best during this trimester.
Third Trimester
Shortness of breath, heartburn, swelling in feet and ankles, Braxton Hicks contractions, difficulty sleeping, and frequent urination. These are normal as your body prepares for delivery.
When to Call Your Doctor
Contact your healthcare provider immediately if you experience:
- Vaginal bleeding or fluid leakage
- Severe or persistent headaches with vision changes
- Severe abdominal pain or cramping
- Decreased fetal movement after 28 weeks
- Signs of preterm labor (regular contractions before 37 weeks)
- High fever (above 100.4°F / 38°C)
Learn more about pregnancy-related health concerns on our Diseases & Conditions and Women's Wellness pages.
Frequently Asked Questions About Pregnancy Due Dates
A due date calculator provides an estimate based on standard gestational timelines. Only about 5% of babies are born on their exact due date. Most babies arrive within a two-week window around the EDD (between 38 and 42 weeks). An early ultrasound (before 12 weeks) can refine the estimate to within 5–7 days of accuracy.
Yes. Your healthcare provider may adjust your due date based on an early ultrasound measurement (crown-rump length). If the ultrasound date differs from the LMP-based date by more than 7 days in the first trimester, the ultrasound date is typically used. Later ultrasounds are less accurate for dating.
If you are unsure of your LMP, you can use the conception date method (if you tracked ovulation) or the IVF transfer date method. Alternatively, your doctor can estimate gestational age through an early ultrasound, which measures the embryo's size to determine how far along you are.
Gestational age is counted from the first day of your last menstrual period (LMP) and is the standard used by healthcare providers. Fetal age (also called conceptional age) is counted from the actual date of conception, which is typically about 2 weeks less than gestational age. A pregnancy at 10 weeks gestational age is approximately 8 weeks fetal age.
According to ACOG, full-term pregnancy is defined as delivery between 39 weeks 0 days and 40 weeks 6 days. Early term is 37–38 weeks, late term is 41 weeks, and post-term is 42 weeks or later. Babies born at full term generally have the best health outcomes.
For IVF pregnancies, the due date is calculated from the embryo transfer date. For a Day 5 blastocyst transfer, 261 days are added to the transfer date. For a Day 3 embryo transfer, 263 days are added. This method is considered the most accurate because the exact date of fertilization is known.
Common signs that labor is approaching include: the baby dropping lower into the pelvis (lightening), increased Braxton Hicks contractions, loss of the mucus plug, water breaking (rupture of membranes), regular contractions that increase in frequency and intensity, lower back pain, and a burst of energy known as "nesting instinct." Contact your healthcare provider when contractions are 5 minutes apart, lasting 1 minute each, for at least 1 hour.