Pregnancy Calculator & Due Date Calculator
Calculate your due date and track your pregnancy week by week with detailed milestones
Your Information
📅 Most accurate for regular 28-day cycles
💡 Tip: If you have irregular cycles or are unsure of your dates, an early ultrasound (dating scan) can provide a more accurate due date.
VitalMetrics - Pregnancy Calculator
11/2/2025
Your Pregnancy
Enter your date above to see your pregnancy details
How the Due Date is Calculated
This calculator uses Naegele's Rule, the standard method used by healthcare providers worldwide to estimate your due date. Developed by German obstetrician Franz Naegele in the early 1800s, this formula has been used for over 200 years.
The Formula:
From Last Menstrual Period (LMP):
Due Date = LMP + 280 days (40 weeks)
From Conception Date:
Due Date = Conception Date + 266 days (38 weeks)
The calculation assumes a regular 28-day menstrual cycle with ovulation occurring on day 14. This is why pregnancy is counted from the first day of your last period, even though conception typically occurs about 2 weeks later.
For women with irregular cycles or cycles that differ from 28 days, an early ultrasound (typically between 8-12 weeks) can provide a more accurate due date based on the baby's measurements.
Understanding Pregnancy Weeks
Why weeks, not months?
Pregnancy is measured in weeks because fetal development happens rapidly and consistently each week. Healthcare providers can more accurately track development and identify potential concerns using weeks rather than the more variable month-by-month system.
The first 2 weeks are unique
Technically, you're not pregnant during weeks 1 and 2. Week 1 is the week of your period, and conception typically occurs at the end of week 2. However, these weeks are included in the pregnancy timeline because they're counted from the first day of your last menstrual period (LMP).
Full-term pregnancy
A full-term pregnancy is considered 37-42 weeks. However, "full term" is now divided into categories:
- Early term: 37-38 weeks
- Full term: 39-40 weeks
- Late term: 41 weeks
- Post term: 42+ weeks
📊 Did you know? Only about 5% of babies arrive exactly on their due date. Most babies are born within 2 weeks before or after the estimated due date. Your due date is an estimate, not a deadline!
Trimester Breakdown
1st Trimester (Weeks 1-12)
The most critical period of development. All major organs and body systems begin forming. This is when the baby is most vulnerable to factors that might affect development.
Key Milestones:
- • Heart begins beating (week 5-6)
- • All major organs start developing
- • Arms, legs, fingers, and toes form
- • First prenatal visit and ultrasound
- • Miscarriage risk drops significantly after week 12
Common symptoms: Morning sickness, fatigue, breast tenderness, frequent urination, mood swings
2nd Trimester (Weeks 13-27)
Often called the "honeymoon period" or "golden trimester" because most women feel their best. Energy returns, morning sickness fades, and you're not yet uncomfortable from the baby's size.
Key Milestones:
- • Feel baby's first movements (quickening) around weeks 16-20
- • Baby bump becomes visible
- • Anatomy scan (detailed ultrasound) around week 20
- • Can often find out baby's sex
- • Baby can hear sounds from outside the womb
Common symptoms: Increased energy, glowing skin, growing belly, baby kicks
3rd Trimester (Weeks 28-40)
The home stretch! Baby gains most of their weight during this time, and their organs mature in preparation for life outside the womb. You'll likely feel more uncomfortable as baby grows.
Key Milestones:
- • Baby's lungs mature
- • Baby gains about 1/2 pound per week
- • Baby moves into head-down position for birth
- • More frequent prenatal checkups (weekly after week 36)
- • Baby is full term at week 37
Common symptoms: Shortness of breath, frequent urination, Braxton Hicks contractions, back pain, swelling, fatigue, nesting instinct
Important Milestones & Appointments
Weeks 8-12: First Prenatal Visit
Dating ultrasound, blood tests, medical history, calculate due date, hear baby's heartbeat with Doppler
Week 12: End of First Trimester
Miscarriage risk drops significantly, morning sickness typically improves, many women announce pregnancy
Weeks 18-22: Anatomy Scan
Detailed ultrasound checking baby's organs and development, often can find out sex, check placenta position
Week 24: Viability Milestone
If born now, baby has a chance of survival with intensive medical care, glucose screening for gestational diabetes
Week 28: Third Trimester Begins
More frequent checkups, monitor for preterm labor, baby's survival rate improves significantly
Week 37: Full Term
Baby is full term and can be born safely, weekly checkups, cervical checks may begin
Accuracy & Limitations
📊 Only 5% of babies arrive on their due date
Your due date is an estimate, not a guarantee. Most babies are born within 2 weeks before or after the estimated due date. Think of it as a "due month" rather than a "due date."
Factors affecting accuracy:
- Irregular menstrual cycles: If your cycles aren't consistently 28 days, the LMP method may be less accurate
- Uncertain LMP date: If you're not sure when your last period started, the calculation will be less reliable
- Breastfeeding or recent birth control: These can affect cycle regularity
- PCOS or hormonal conditions: May cause irregular ovulation
More accurate methods:
- Early ultrasound (8-12 weeks): Most accurate method for dating a pregnancy. Measures baby's size to estimate gestational age
- IVF or known conception date: If you know exactly when conception occurred (such as with IVF), the due date can be calculated very precisely
💡 Remember: Every pregnancy is unique. Your baby will arrive when they're ready. The actual delivery window for a full-term pregnancy is 37-42 weeks, giving you a 5-week range!
Frequently Asked Questions
⚠️ Medical Disclaimer
This pregnancy calculator is for informational and educational purposes only. It is not a substitute for professional medical advice, diagnosis, prenatal care, or treatment.
Always consult with your healthcare provider if you experience:
- • Severe abdominal pain or cramping
- • Vaginal bleeding or fluid leakage
- • Severe headaches or vision changes
- • Sudden swelling of face, hands, or feet
- • Decreased baby movement (after week 28)
- • Contractions before 37 weeks
- • Fever, chills, or signs of infection
Regular prenatal care is essential. Attend all scheduled appointments with your healthcare provider for proper monitoring of you and your baby's health throughout pregnancy.