Pregnancy Calculator - Calculate Your Due Date & Pregnancy Timeline

What is a Pregnancy Calculator?

A pregnancy calculator is a free online tool that helps you calculate your estimated due date, current pregnancy week, trimester, and important pregnancy milestones based on either your last menstrual period (LMP) or conception date. Whether you just discovered you're pregnant, planning pregnancy, or simply curious about your baby's development timeline, our pregnancy calculator provides accurate estimates for due dates, prenatal appointment schedules, and fetal development stages throughout your pregnancy journey.

How to Use the Pregnancy Calculator

Calculating your pregnancy timeline is simple:

1. Choose Calculation Method: Select either "Last Menstrual Period" or "Conception Date"
2. Enter Date: Input your LMP first day or known conception date
3. Add Cycle Length (if using LMP): Enter your average cycle length (default is 28 days)
4. Calculate: Click to generate your pregnancy timeline
5. View Due Date: See your estimated delivery date (EDD)
6. Check Current Week: Find out how many weeks pregnant you are
7. See Trimester: Identify which trimester you're currently in
8. Review Milestones: View important dates for appointments and development

Understanding Pregnancy Dating

How Pregnancy is Calculated

Pregnancy is calculated from the first day of your last menstrual period (LMP), not from conception. This method is used because most women know when their last period started, but the exact conception date is often unknown.

Standard Pregnancy Length: 40 weeks (280 days) from LMP

Actual Gestation: ~38 weeks from conception

Why the Difference: Ovulation typically occurs around day 14 of your cycle

Why Use LMP Dating?

• Universal Standard: Medical professionals worldwide use this method
• Easy to Track: Most women remember their last period
• Standardized Care: Prenatal schedules based on LMP dating
• Consistent Measurements: Allows comparison of fetal development

Conception Date Method

If you know your conception date (through fertility tracking, IVF, or accurate ovulation tracking), you can calculate more precisely by adding 266 days (38 weeks) to that date.

Pregnancy Trimesters Explained

First Trimester (Weeks 1-12)

Duration: Weeks 1-12 (Months 1-3)

Key Developments:

• Neural tube forms (brain and spinal cord)
• Heart begins beating (week 6)
• Major organs start developing
• Limbs and facial features form
• Baby grows from embryo to fetus

Common Symptoms:

• Morning sickness and nausea
• Fatigue and exhaustion
• Breast tenderness
• Frequent urination
• Food aversions or cravings
• Mood swings

Important Milestones:

• First prenatal visit (8-10 weeks)
• First ultrasound (8-12 weeks)
• Hear heartbeat (10-12 weeks)
• End of highest miscarriage risk period

Second Trimester (Weeks 13-26)

Duration: Weeks 13-26 (Months 4-6)

Key Developments:

• Baby's movements felt (quickening around 18-20 weeks)
• Sex can often be determined (18-20 weeks)
• Baby hears sounds
• Develops sleep/wake cycles
• Rapid growth period
• Fingerprints form

Common Symptoms:

• Energy returns ("honeymoon period")
• Baby bump becomes visible
• Reduced nausea
• Back pain may begin
• Skin changes (linea nigra, melasma)
• Round ligament pain

Important Milestones:

• Anatomy scan (18-22 weeks)
• Feel baby's first movements
• Glucose screening (24-28 weeks)
• Start feeling baby kicks regularly

Third Trimester (Weeks 27-40+)

Duration: Weeks 27-40+ (Months 7-9+)

Key Developments:

• Baby's lungs mature
• Eyes open and close
• Baby gains most of their weight
• Brain develops rapidly
• Baby assumes head-down position (usually by week 36)
• Full-term at 37 weeks

Common Symptoms:

• Increased fatigue
• Frequent urination returns
• Shortness of breath
• Braxton Hicks contractions
• Swelling in feet and ankles
• Difficulty sleeping
• Back and pelvic pain

Important Milestones:

• Weekly appointments begin (36 weeks)
• Group B strep test (35-37 weeks)
• Baby "drops" into pelvis
• Full-term reached (37 weeks)
• Due date (40 weeks)

Important Pregnancy Milestones & Dates

Early Pregnancy

• 4 weeks: Positive pregnancy test possible
• 6 weeks: Heartbeat detectable on ultrasound
• 8-10 weeks: First prenatal appointment
• 10-12 weeks: First trimester screening, NT scan
• 12 weeks: End of first trimester, miscarriage risk drops significantly

Mid Pregnancy

• 16 weeks: Amniocentesis option (if needed)
• 18-20 weeks: Anatomy ultrasound, gender reveal possible
• 20 weeks: Halfway point!
• 24 weeks: Viability milestone (baby could survive with intensive care)
• 24-28 weeks: Glucose screening for gestational diabetes

Late Pregnancy

• 28 weeks: Third trimester begins
• 32 weeks: Baby typically head-down
• 36 weeks: Weekly appointments begin
• 37 weeks: Early term (baby considered full-term)
• 39-40 weeks: Full term
• 40 weeks: Due date (only 5% deliver exactly on this date)
• 41-42 weeks: Late term, induction often recommended

Frequently Asked Questions (FAQs)

How accurate is the pregnancy calculator?

The calculator provides an estimate based on standard 40-week pregnancies. Your actual due date may vary by 1-2 weeks. Only about 5% of babies arrive on their exact due date. Ultrasound measurements in early pregnancy (before 13 weeks) provide the most accurate dating.

When should I take a pregnancy test?

Most home pregnancy tests are accurate on the first day of your missed period (about 14 days after conception). Some sensitive tests can detect pregnancy 10-12 days after conception. Testing too early may give false negatives.

How many weeks pregnant am I?

Count from the first day of your last menstrual period, not from conception. If your LMP was 8 weeks ago, you're 8 weeks pregnant. Use our calculator for an exact count including days.

What is the difference between gestational age and fetal age?

Gestational age counts from your LMP (what doctors use). Fetal age counts from conception, typically 2 weeks less than gestational age. Medical professionals use gestational age for consistency.

Can my due date change?

Yes. Your due date may be adjusted after your first ultrasound if the baby's measurements suggest conception occurred earlier or later than calculated from your LMP. First-trimester ultrasounds are most accurate for dating.

What if I have irregular periods?

If your cycles are irregular or longer/shorter than 28 days, LMP dating may be less accurate. Early ultrasound measurements (6-12 weeks) will provide more accurate dating. Inform your healthcare provider about irregular cycles.

When will I feel the baby move?

First-time mothers typically feel movement (quickening) around 18-20 weeks. Women who've been pregnant before may feel it as early as 16 weeks. Initial movements feel like flutters, bubbles, or gentle taps.

What does full-term mean?

Full-term pregnancy is now divided into categories: early term (37-38 weeks), full term (39-40 weeks), and late term (41 weeks). Babies born at 39-40 weeks have the best outcomes. Post-term is 42+ weeks.

How is my due date determined at the doctor?

Your doctor uses your LMP initially, then confirms or adjusts based on early ultrasound measurements. The most accurate measurements come from ultrasounds done between 8-13 weeks of pregnancy.

Can I calculate my due date from conception date?

Yes! If you know your conception date (fertility tracking, IVF, or accurate ovulation tracking), add 266 days (38 weeks) to that date. This method is often more accurate than LMP dating.

What is Naegele's Rule?

Naegele's Rule is the formula for calculating due dates: Take the first day of your LMP, add 7 days, subtract 3 months, and add 1 year. Our calculator uses this rule adjusted for your cycle length.

When should I tell people I'm pregnant?

Many couples wait until after the first trimester (12 weeks) when miscarriage risk decreases significantly. However, there's no right answer—tell people when you feel comfortable.

How often will I have prenatal appointments?

Typical schedule: every 4 weeks until 28 weeks, every 2 weeks from 28-36 weeks, then weekly from 36 weeks until delivery. High-risk pregnancies may require more frequent visits.

What if I go past my due date?

Most doctors allow pregnancies to continue to 41-42 weeks with monitoring. Induction is typically recommended by 41-42 weeks to prevent complications. Discuss your provider's protocol during pregnancy.

Can I change my due date?

Healthcare providers may adjust your due date based on early ultrasound measurements if there's a significant discrepancy (more than 5-7 days) from LMP dating. After 20 weeks, due dates are rarely changed.

Prenatal Appointment Schedule

First Trimester Appointments

6-8 Weeks: Confirmation appointment

• Confirm pregnancy
• Medical history review
• Initial physical exam
• Blood tests (blood type, Rh factor, immunity screening)
• Discuss prenatal vitamins

10-12 Weeks: First major appointment

• Hear baby's heartbeat
• First ultrasound (dating scan)
• First-trimester screening (optional)
• NT scan (nuchal translucency)
• NIPT blood test option (non-invasive prenatal testing)

Second Trimester Appointments

Every 4 Weeks: Routine checkups

• Blood pressure and weight monitoring
• Measure fundal height
• Listen to heartbeat
• Address concerns

16 Weeks: Quad screen (optional)

• Blood test for neural tube defects and chromosomal abnormalities

18-20 Weeks: Anatomy scan

• Detailed ultrasound
• Check baby's development
• Gender reveal (if desired)
• Check placenta position

24-28 Weeks: Glucose screening

• Test for gestational diabetes
• Rhogam shot if Rh-negative

Third Trimester Appointments

28-36 Weeks: Every 2 weeks

• Monitor baby's growth
• Check position
• Discuss birth plan
• Review signs of labor

35-37 Weeks: Group B strep test

• Vaginal/rectal swab
• Determines antibiotic need during labor

36+ Weeks: Weekly appointments

• Cervical checks (if desired)
• Monitor for labor signs
• Discuss delivery details
• NST (non-stress test) if needed

Week-by-Week Pregnancy Highlights

Weeks 4-8: Early Development

• Week 4: Implantation occurs, pregnancy test positive
• Week 5: Heart starts forming
• Week 6: Neural tube closes, heartbeat begins
• Week 7: Arm and leg buds appear
• Week 8: All major organs begin forming

Weeks 9-13: End of First Trimester

• Week 9: Baby is officially a fetus
• Week 10: Vital organs functioning
• Week 11: Baby can open and close fists
• Week 12: Reflexes developing
• Week 13: Second trimester begins

Weeks 14-27: Growth & Movement

• Week 16: Baby's sex may be visible on ultrasound
• Week 18: Baby hears sounds
• Week 20: Halfway point! Anatomy scan
• Week 24: Viability milestone
• Week 27: Third trimester begins

Weeks 28-40: Final Preparations

• Week 32: Baby usually head-down
• Week 36: Baby considered early term if born
• Week 37: Full-term begins
• Week 39-40: Optimal delivery window
• Week 40: Due date!

Baby Size Comparisons by Week

First Trimester

• Week 4: Poppy seed (2mm)
• Week 8: Raspberry (1.6cm)
• Week 12: Lime (5.4cm)

Second Trimester

• Week 16: Avocado (11.6cm)
• Week 20: Banana (25.6cm)
• Week 24: Ear of corn (30cm)

Third Trimester

• Week 28: Eggplant (37.6cm)
• Week 32: Squash (42.4cm)
• Week 36: Romaine lettuce (47.4cm)
• Week 40: Small watermelon (51.2cm)

Signs of Labor to Watch For

Pre-Labor Signs (Days to Weeks Before)

• Baby "drops" lower into pelvis (lightening)
• Increased Braxton Hicks contractions
• Cervical changes (dilation, effacement)
• Weight loss (1-3 pounds)
• Increased discharge
• Burst of energy (nesting instinct)

True Labor Signs (Call Your Provider)

• Regular contractions (increasing in frequency and intensity)
• Contractions 5 minutes apart, lasting 1 minute, for 1 hour (5-1-1 rule)
• Water breaks (rupture of membranes)
• Bloody show (mucus plug discharge with blood)
• Severe back pain with contractions
• Pressure in pelvis/rectum

Emergency Signs (Go to Hospital Immediately)

• Heavy vaginal bleeding
• Sudden severe headache with vision changes
• Decreased fetal movement
• Signs of infection (fever over 100.4°F)
• Severe abdominal pain
• Water breaks with greenish or brown color

Pregnancy Planning Tips

Before Pregnancy

• Start prenatal vitamins with folic acid (400-800mcg daily)
• Visit your doctor for preconception checkup
• Update vaccinations if needed
• Achieve healthy weight
• Review medications with doctor
• Reduce alcohol, quit smoking
• Track menstrual cycles

During Pregnancy

• Attend all prenatal appointments
• Take prenatal vitamins daily
• Stay hydrated (8-10 glasses of water)
• Exercise moderately (if approved by doctor)
• Eat balanced, nutritious diet
• Get adequate rest
• Avoid alcohol, smoking, and drugs
• Limit caffeine (under 200mg daily)
• Practice stress management

Preparing for Baby

• Choose healthcare provider for baby (pediatrician)
• Take childbirth education classes
• Tour hospital or birth center
• Prepare nursery
• Pack hospital bag (by 36 weeks)
• Install car seat (by 37 weeks)
• Write birth plan
• Prepare siblings (if applicable)

Calculating Conception Date

From Due Date

Subtract 266 days (38 weeks) from your due date to estimate conception.

Example: Due date is January 1, 2026
Conception date: approximately April 10, 2025

From LMP

Add 14 days to the first day of your LMP (for average 28-day cycle).

Example: LMP started March 27, 2025
Conception date: approximately April 10, 2025

Fertility Window

Conception typically occurs during a 6-day window: 5 days before ovulation through the day of ovulation. Sperm can survive up to 5 days, while eggs survive 12-24 hours.

When to Call Your Healthcare Provider

First Trimester Concerns

• Heavy bleeding with cramping
• Severe abdominal pain
• Fever over 100.4°F
• Severe vomiting (unable to keep fluids down)
• Pain during urination
• Sudden severe headache

Second/Third Trimester Concerns

• Decreased fetal movement
• Regular contractions before 37 weeks
• Water breaking before 37 weeks
• Vaginal bleeding
• Severe swelling of face/hands
• Vision changes or severe headache
• Signs of preterm labor

Routine Questions (Can Wait for Next Appointment)

• Mild discomfort or aches
• General pregnancy questions
• Nutrition concerns
• Exercise questions
• Minor symptoms

Understanding Your Due Date Window

Due Date Statistics

• Only 5%: Deliver exactly on due date
• 70%: Deliver within 10 days of due date
• 90%: Deliver between 37-42 weeks

Term Classifications

• Early Term: 37-38 weeks 6 days
• Full Term: 39-40 weeks 6 days
• Late Term: 41-41 weeks 6 days
• Post Term: 42 weeks and beyond

Why Due Dates Vary

• Cycle length variations
• Ovulation timing differences
• Individual baby development
• Placental function
• Genetic factors
• First vs. subsequent pregnancies

Pregnancy Nutrition & Health

Essential Nutrients

• Folic Acid: 600-800mcg daily (prevents neural tube defects)
• Iron: 27mg daily (prevents anemia)
• Calcium: 1,000mg daily (bone development)
• DHA: 200-300mg daily (brain development)
• Vitamin D: 600 IU daily (bone health)
• Protein: 75-100g daily (growth and development)

Foods to Avoid

• Raw or undercooked meat, eggs, seafood
• Unpasteurized dairy products
• High-mercury fish (swordfish, shark, king mackerel)
• Deli meats (unless heated to steaming)
• Raw sprouts
• Unwashed produce
• Excessive caffeine (limit to 200mg/day)
• Alcohol (no safe amount during pregnancy)

Safe Exercise During Pregnancy

• Walking
• Swimming
• Prenatal yoga
• Stationary cycling
• Low-impact aerobics
• Avoid: contact sports, activities with fall risk, hot yoga, scuba diving