Due Date Calculator
Calculate your estimated due date using your last menstrual period, conception date, or ultrasound. Track your pregnancy weeks, trimester, and key developmental milestones.
Pregnancy Due Date Calculator
How Would You Like to Calculate?
Your Pregnancy Timeline
Pregnancy Timeline
Key Pregnancy Milestones
Pregnancy Week by Week Guide
| Trimester | Weeks | Key Developments |
|---|---|---|
| First | 1-13 | Conception, embryo development, heart starts beating, major organs form |
| Second | 14-27 | Baby grows rapidly, movement felt, gender visible, hair grows |
| Third | 28-40 | Brain development, lungs mature, baby gains weight, prepares for birth |
Due Date Quick Facts
Important Dates
Conception & Ovulation
Calculation Methods
LMP + 280 days (40 weeks) = Due Date
Conception Date + 266 days (38 weeks) = Due Date
Most accurate early in pregnancy (8-12 weeks)
LMP - 3 months + 7 days + 1 year
Due Date Calculator: Estimate Your Baby's Arrival
Our due date calculator helps expectant parents estimate their baby's arrival date using multiple methods. Whether you know your last menstrual period, conception date, or have ultrasound measurements, this pregnancy calculator provides accurate due date estimation and tracks your pregnancy progress.
Understanding your estimated due date (EDD) is crucial for prenatal care, preparing for baby's arrival, and tracking developmental milestones. This pregnancy due date predictor uses Naegele's Rule and other validated methods to provide reliable estimates.
How Is a Due Date Calculated?
LMP Method
The most common method. Count 280 days (40 weeks) from the first day of your last menstrual period. This assumes a 28-day cycle with ovulation on day 14.
Conception Method
If you know the exact date of conception (ovulation), add 266 days (38 weeks). This is typically 2 weeks after LMP for a 28-day cycle.
Ultrasound Method
Uses fetal measurements to estimate gestational age. Most accurate when done between 8-12 weeks of pregnancy.
Understanding Your Pregnancy Timeline
Key Pregnancy Milestones
Week 6-8
Baby's heart begins to beat. Major organs start forming.
Week 12
End of first trimester. Risk of miscarriage significantly decreases.
Week 18-20
Gender can often be determined. Baby's movements felt (quickening).
Week 28
Third trimester begins. Baby's brain develops rapidly.
Week 37
Considered "early term." Baby is ready for birth any time now.
Week 40
Estimated due date. Only 5% of babies arrive on this exact date.
Frequently Asked Questions (FAQ)
How accurate is the due date calculator?
Due date calculators provide an estimate, not a guarantee. The accuracy depends on the method used:
• LMP Method: ~70% accurate within 1 week
• Conception Method: More accurate if you know the exact date
• Ultrasound: Most accurate (within 2-5 days) when done at 8-12 weeks
Important: Only 5% of babies are born on their exact due date. Most arrive within 2 weeks before or after.
What is Naegele's Rule?
Naegele's Rule is the standard method for calculating due dates:
Formula: LMP - 3 months + 7 days + 1 year
Example: If LMP was January 1, 2024:
January 1 - 3 months = October 1, 2023
October 1 + 7 days = October 8, 2023
October 8 + 1 year = October 8, 2024
This assumes a 28-day cycle. Adjustments may be needed for irregular cycles.
How are pregnancy weeks counted?
Pregnancy is counted from the first day of your last menstrual period (LMP), not from conception.
Example:
• LMP: January 1
• Conception: January 14 (day 14)
• You're considered "2 weeks pregnant" on January 14
This means the first 2 weeks of pregnancy occur before you actually conceive! This is why pregnancy is measured as 40 weeks (LMP method) but conception to birth is only 38 weeks.
What is the fertile window?
The fertile window is the time when pregnancy is most likely to occur:
• Timing: 5 days before ovulation + ovulation day
• Best chance: Having sex 1-2 days before ovulation
• Sperm survival: Up to 5 days in the reproductive tract
• Egg survival: Up to 24 hours after ovulation
For a 28-day cycle, ovulation typically occurs on day 14, making the fertile window days 9-14.
What happens if my due date passes?
If you pass your due date (post-term pregnancy):
• Weeks 40-41: Most doctors recommend monitoring with non-stress tests
• Week 41: Induction is often considered
• Week 42+: Increased risks, usually induced
Statistics:
• 50% of first-time mothers deliver by week 40+5
• 75% deliver by week 41+2
• 95% deliver by week 42
Always consult your healthcare provider for personalized guidance.
How does ovulation affect due date calculation?
Ovulation date is key to accurate due date calculation:
Standard assumption: Ovulation on day 14 of a 28-day cycle
If you know ovulation date:
• Conception occurs within 24 hours of ovulation
• Due date = Ovulation date + 266 days
• This is more accurate than LMP method for irregular cycles
Ovulation predictor kits (OPKs): Help determine ovulation for more precise dating
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