Calculators
Pregnancy Due Date Calculator
Calculate your pregnancy due date, current week, trimester, and baby development milestones. Get accurate pregnancy timeline based on last menstrual period or conception date.
Use Pregnancy Due Date Calculator to get instant results without uploads or sign-ups. Everything runs securely in your browser for fast, reliable output.
Your results will appear here.
About this tool
Pregnancy typically lasts 280 days (40 weeks) from the first day of your last menstrual period (LMP), though only about 5% of babies arrive exactly on their due date. Our Pregnancy Due Date Calculator uses the standard Naegele's Rule, which adds 280 days to your LMP, or 266 days from conception date. This is the same method used by healthcare providers worldwide. The calculator accounts for different cycle lengths - if your cycle is shorter or longer than the standard 28 days, it adjusts the due date accordingly for better accuracy.
Understanding your pregnancy timeline is essential for proper prenatal care. The first trimester (weeks 1-12) is critical for organ development and highest miscarriage risk. The second trimester (weeks 13-26) is often called the "golden period" with more energy and less nausea. The third trimester (weeks 27-40) involves rapid growth and preparation for birth. Our calculator shows exactly which week and trimester you're in, when each trimester begins and ends, and key developmental milestones happening with your baby right now.
Pregnancy dating is most accurate when based on early ultrasound measurements (7-13 weeks), which can date pregnancy within 3-5 days accuracy. LMP-based calculations can vary if you have irregular cycles, conceived while breastfeeding, or recently stopped birth control. Healthcare providers often adjust due dates based on first-trimester ultrasound measurements. Our calculator provides the standard LMP-based estimate that your doctor will use as a starting point. Remember that only 4-5% of babies arrive on their exact due date - delivery anywhere from 37-42 weeks is considered full term.
The calculator also provides helpful information about prenatal testing schedules, approximate conception date (useful for partner confirmation), and fetal development stages. All calculations are performed privately in your browser - no pregnancy data is stored, transmitted, or shared. You can use this calculator as many times as needed throughout your pregnancy to track progress and plan for important milestones like prenatal tests, baby showers, and maternity leave.
Usage examples
Standard 28-Day Cycle Pregnancy
Last period: January 1st, 28-day cycle, calculated on March 1st
Due Date: October 8th. Current: 8 weeks 5 days pregnant (first trimester). Conception likely occurred around January 15th. Baby is now about the size of a raspberry with developing features. First prenatal appointment recommended around week 8-10. Second trimester begins June 23rd.
Longer Cycle Adjustment
Last period: February 1st, 35-day cycle (7 days longer than standard)
Due Date: November 15th (7 days later than standard calculation). Standard 28-day calculation would give November 8th, but longer cycle means ovulation occurred later. Current: 12 weeks 3 days. First trimester ends around April 25th. This adjustment provides more accurate dating.
Known Conception Date
Conception date: March 10th (IVF or known date)
Due Date: December 1st (266 days from conception). Current: 20 weeks 0 days. This is more accurate than LMP method when conception date is certain. Anatomy scan typically scheduled around 18-22 weeks. Currently in second trimester, which ends July 29th.
Early Pregnancy Detection
Last period: April 1st, testing on April 25th
Due Date: January 6th. Current: 3 weeks 3 days pregnant. Many pregnancy tests show positive around this time. Baby is an embryo smaller than a grain of rice. Heartbeat may be detectable via ultrasound in 2-3 weeks. First prenatal appointment typically scheduled for week 8-10.
Third Trimester Planning
Last period: January 15th, calculated on September 1st
Due Date: October 22nd. Current: 33 weeks 1 day. Third trimester (started August 17th). Baby weighs about 4-5 pounds. Weekly checkups typically begin at 36 weeks. Full term at 37 weeks (October 1st). Planning maternity leave and hospital bag now is recommended.
How to use
- Select your calculation method: Last Menstrual Period (LMP) or Conception Date
- Enter the first day of your last menstrual period (most common method)
- Alternatively, enter the conception date if you know it
- Enter your average cycle length (typically 28 days)
- Click "Calculate" to see your complete pregnancy timeline
- View your estimated due date and current pregnancy week
- See which trimester you're in and when it ends
- Review baby development milestones for your current week
- Check important upcoming prenatal appointment dates
- Save or bookmark your results for future reference
Benefits
- Uses standard Naegele's Rule method recommended by healthcare providers
- Calculates from either last menstrual period or conception date
- Adjusts for non-standard cycle lengths (24-35 days)
- Shows exact pregnancy week and day (e.g., 12 weeks 3 days)
- Displays current trimester with start/end dates for each
- Provides baby development milestones for current week
- Estimates conception date for partner confirmation
- Shows when to schedule important prenatal appointments
- Calculates full-term date range (37-42 weeks)
- Complete privacy - no data stored or transmitted
- No registration or personal information required
- Works on all devices with instant calculations
- Free forever with comprehensive pregnancy information
FAQs
How accurate is this pregnancy due date calculator?
The calculator uses Naegele's Rule, the standard medical formula that estimates due dates within 7-10 days accuracy for women with regular cycles. However, only 4-5% of babies arrive on their exact due date. Most babies (about 80%) are born within 2 weeks before or after the due date. First-trimester ultrasound (7-13 weeks) is the most accurate dating method, precise within 3-5 days. If your cycles are irregular, you recently stopped birth control, or were breastfeeding when you conceived, ultrasound dating is more reliable than LMP calculations.
Should I calculate from my last period or conception date?
Calculate from your last menstrual period (LMP) if you're unsure of conception date - this is what doctors use as standard. The first day of your last period is "day 1" of pregnancy even though conception occurs around day 14. Use conception date if you know it precisely (from IVF, fertility tracking, or single intercourse occasion). Conception date calculation adds 266 days, while LMP adds 280 days (14 days difference accounts for time before ovulation). If both dates are known, doctors typically trust early ultrasound measurements most for due date accuracy.
What if my cycle is not 28 days?
Enter your actual cycle length in the calculator for better accuracy. If you have a 35-day cycle, you ovulate around day 21 (not day 14), so conception occurs a week later and your due date should be adjusted 7 days later. Shorter cycles (24-26 days) mean earlier ovulation and earlier due dates. The calculator automatically adjusts for this. However, if your cycles are very irregular (varying by more than 7 days), LMP calculations are less reliable. Ultrasound dating in the first trimester becomes even more important for accuracy in these cases.
When do the three trimesters begin and end?
First trimester: Weeks 1-12 (conception through 12 weeks 6 days). This is the crucial organ development period with highest miscarriage risk (10-20%). Second trimester: Weeks 13-26 (often the easiest period with more energy, less nausea). Third trimester: Weeks 27-40+ (rapid growth, preparing for birth). Some medical organizations use slightly different cutoffs (0-13, 14-27, 28-40), but 1-12, 13-26, 27-40 is most common. Each trimester brings different developmental milestones, symptoms, and prenatal care requirements.
What does "full term" mean?
Full term is now classified with more precision: Early term (37-38 weeks 6 days), Full term (39-40 weeks 6 days), Late term (41-41 weeks 6 days), and Post term (42+ weeks). Babies born at 39-40 weeks have the best outcomes with lowest risks. Before 37 weeks is preterm (premature). After 42 weeks is post-term and typically doctors will induce labor due to increased risks. The traditional "due date" is 40 weeks, but normal delivery anytime between 37-42 weeks is considered healthy. Most providers induce by 41-42 weeks if labor hasn't started naturally.
When will I first feel baby move?
First-time mothers typically feel movement (called "quickening") between 18-25 weeks, most commonly around 20 weeks. Women who've been pregnant before often feel movement earlier, around 16-18 weeks, because they recognize the sensation. Early movements feel like flutters, butterflies, or gas bubbles. By 24-28 weeks, movements become stronger kicks and rolls that others can feel by touching your belly. Movement patterns become more regular in third trimester. Decreased movement after 28 weeks should always be reported to your healthcare provider immediately.
When should I schedule prenatal appointments?
First appointment: 8-10 weeks (confirms pregnancy, dates pregnancy via ultrasound, initial labs). Then monthly visits until 28 weeks. Bi-weekly visits from 28-36 weeks. Weekly visits from 36 weeks until delivery. Key appointments include: 10-13 weeks (possible NT scan for genetic screening), 15-20 weeks (quad screen blood test), 18-22 weeks (anatomy scan ultrasound), 24-28 weeks (glucose test for gestational diabetes), 35-37 weeks (Group B strep test). Your provider may recommend more frequent visits if you're high-risk or have complications.
Can my due date change?
Yes, due dates are often adjusted based on first-trimester ultrasound measurements (7-13 weeks), which are accurate within 3-5 days. If ultrasound dating differs from LMP dating by more than 5-7 days, doctors typically use the ultrasound date. Due dates are adjusted in about 20% of pregnancies. After the first trimester, due dates should NOT be changed based on ultrasound - later ultrasounds measure growth, not age, and growth varies significantly. Once your due date is set after first-trimester ultrasound, it typically remains the official date unless special circumstances arise.
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