Pregnancy Calculator
Calculate your pregnancy weeks and due date
This is the first day of your last period before conception
How to Use This Calculator
- • Enter the first day of your last menstrual period
- • The calculator uses the standard 280-day pregnancy
- • Results are estimates - consult your healthcare provider
- • Due dates can vary by ±2 weeks naturally
Enter your last menstrual period date to calculate pregnancy progress
Pregnancy is typically calculated from the first day of your last menstrual period (LMP), not from the date of conception. This method, used by healthcare providers worldwide, provides a standardized way to track pregnancy progress and estimate due dates.
Why Calculate from Last Menstrual Period?
While it might seem logical to calculate pregnancy from conception, the exact date of conception is often unknown. The LMP method provides a reliable reference point because:
- Most women remember their last period date
- It provides a consistent calculation method
- Medical research and guidelines are based on this system
- Ultrasound measurements align with LMP dating
Understanding Pregnancy Duration
A full-term pregnancy lasts approximately 280 days (40 weeks) from the LMP. This is divided into three trimesters, each with distinct characteristics and developmental milestones.
The Three Trimesters
First Trimester (Weeks 1-13)
The first trimester is crucial for organ development. During this period, the baby's major organs and body systems begin to form.
Key Developments:
- Weeks 1-2: Fertilization and implantation occur
- Week 4: Neural tube (future spinal cord) forms
- Week 6: Heart begins to beat
- Week 8: All major organs are present
- Week 12: Baby is fully formed but needs to grow
Common Symptoms:
- Morning sickness and nausea
- Breast tenderness
- Fatigue
- Frequent urination
- Food aversions or cravings
Second Trimester (Weeks 14-27)
Often called the "golden period" of pregnancy, the second trimester typically brings relief from early pregnancy symptoms and increased energy.
Key Developments:
- Week 16: Baby's sex can be determined
- Week 18-20: Anatomy scan ultrasound
- Week 20: You may feel first movements (quickening)
- Week 24: Baby's hearing is developing
- Week 26: Eyes begin to open
Common Changes:
- Visible baby bump appears
- Improved energy levels
- Reduced nausea
- Skin and hair changes
- Weight gain becomes more noticeable
Third Trimester (Weeks 28-40)
The final stretch focuses on growth and maturation as the baby prepares for life outside the womb.
Key Developments:
- Week 28: Baby's brain develops rapidly
- Week 32: Bones harden (except skull)
- Week 36: Lungs are nearly mature
- Week 37: Baby is considered full-term
- Week 40: Due date arrives
Common Experiences:
- Increased baby movements
- Braxton Hicks contractions
- Shortness of breath
- Frequent urination returns
- Nesting instinct
Important Pregnancy Milestones
First Prenatal Appointment (Week 8-12)
Your first prenatal visit typically occurs between 8-12 weeks. This comprehensive appointment includes:
- Medical history review
- Physical examination
- Blood tests and screenings
- Due date confirmation
- Prenatal vitamin recommendations
Genetic Screening (Weeks 10-13 and 15-20)
Optional screening tests can assess the risk of genetic conditions:
- First trimester screening: Blood test and ultrasound
- Second trimester screening: Additional blood tests
- Non-invasive prenatal testing (NIPT): Advanced screening option
Anatomy Scan (Weeks 18-22)
This detailed ultrasound examines the baby's development and can reveal:
- Baby's sex (if desired)
- Organ development
- Growth measurements
- Placenta position
- Amniotic fluid levels
Due Date Accuracy
While our calculator provides an estimated due date, it's important to understand that:
- Only about 5% of babies are born on their exact due date
- Most babies are born within 2 weeks of the due date
- First-time mothers often deliver after their due date
- Ultrasound dating may adjust your due date
Factors That Can Affect Due Date Calculation
Irregular Menstrual Cycles
If you have irregular periods, LMP dating may be less accurate. Your healthcare provider may rely more heavily on ultrasound measurements for dating.
Conception Date Knowledge
If you know your exact conception date (from fertility treatments, for example), your provider may adjust the due date accordingly.
Early Ultrasound Measurements
First-trimester ultrasounds are very accurate for dating and may lead to due date adjustments if they differ significantly from LMP dating.
Healthy Pregnancy Tips
Nutrition and Supplements
- Take prenatal vitamins with folic acid
- Eat a balanced diet rich in fruits, vegetables, and whole grains
- Consume adequate protein and calcium
- Stay hydrated with plenty of water
- Limit caffeine and avoid alcohol
Lifestyle Considerations
- Get regular, moderate exercise (as approved by your doctor)
- Aim for 7-9 hours of sleep per night
- Manage stress through relaxation techniques
- Avoid smoking and secondhand smoke
- Limit exposure to harmful chemicals
Regular Prenatal Care
Consistent prenatal care is crucial for monitoring both maternal and fetal health:
- First trimester: Monthly appointments
- Second trimester: Every 4 weeks
- Third trimester: Every 2 weeks, then weekly near due date
When to Contact Your Healthcare Provider
Seek immediate medical attention for:
- Severe abdominal pain or cramping
- Heavy bleeding or bright red bleeding
- Severe headaches or vision changes
- Persistent vomiting
- Signs of preterm labor
- Decreased fetal movement (after 28 weeks)
- Signs of infection (fever, chills)
Preparing for Your Baby
Second Trimester Preparations
- Start thinking about baby names
- Begin researching pediatricians
- Consider prenatal classes
- Start planning the nursery
- Discuss maternity leave plans
Third Trimester Preparations
- Pack your hospital bag
- Install the car seat
- Complete the nursery setup
- Finalize birth plan preferences
- Stock up on newborn essentials
Understanding Labor Signs
As you approach your due date, watch for these signs of labor:
- Regular contractions: Becoming stronger and closer together
- Water breaking: Rupture of amniotic membranes
- Bloody show: Loss of mucus plug
- Back pain: Persistent lower back pain
- Nesting urge: Sudden burst of energy to prepare
Remember
This calculator provides estimates based on standard pregnancy calculations. Every pregnancy is unique, and your healthcare provider is the best source for personalized information about your pregnancy progress. Regular prenatal care ensures the best outcomes for both you and your baby.
If you have questions about your pregnancy timeline, symptoms, or any concerns, don't hesitate to contact your healthcare provider. They can provide guidance tailored to your specific situation and medical history.