Due Date Calculator - Pregnancy Timeline & Estimated Delivery Date

Calculate your estimated due date using LMP, conception date, IVF transfer, or ultrasound. Track pregnancy milestones, trimesters, and get accurate delivery date predictions with our comprehensive pregnancy calculator.

Due Date Calculation
Calculate your estimated due date using various methods

Last Menstrual Period Method

Your Pregnancy Timeline
Estimated due date and current pregnancy status

Enter your information to calculate your due date

Understanding Due Date Calculations
Learn about different methods and accuracy

Calculation Methods

Last Menstrual Period
Naegele's Rule: Adds 280 days to the first day of your last period. Most commonly used method.
Ultrasound Dating
Most accurate when done in the first trimester. Can determine gestational age within 3-5 days.
Conception Date
If you know the exact conception date, add 266 days. Useful for IVF or tracked ovulation.
IVF Transfer
Precise calculation based on embryo age at transfer. Most accurate for assisted reproduction.

Accuracy Considerations

  • •Only about 5% of babies are born on their exact due date
  • •Most babies (90%) arrive within two weeks of the due date
  • •First pregnancies often go past the due date
  • •Regular cycles make LMP calculations more accurate
Calculation History
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Medical Note: This calculator provides estimates for educational purposes. Always consult with your healthcare provider for personalized pregnancy care and accurate dating based on your specific situation.

Understanding Pregnancy Due Dates

Your estimated due date (EDD) represents the expected completion of 40 weeks of pregnancy, calculated from the first day of your last menstrual period. While this date serves as an important reference point for prenatal care and birth preparation, it's essential to understand that it's an estimate - only about 5% of babies arrive on their exact due date. The due date helps healthcare providers track fetal development, schedule important tests, and identify potential concerns. Understanding how due dates are calculated using different calculation methods and recognizing the normal range of delivery timing helps set realistic expectations. Learn about your pregnancy timeline and key milestones throughout your journey.

📅 40 Weeks Total

Standard pregnancy duration counted from first day of last period, including 2 weeks before conception.

🎯 5% Accuracy

Only 5% deliver on due date, but 90% deliver within 2 weeks before or after.

👶 38 Weeks Growth

Actual fetal development is 38 weeks from conception to full term.

📊 Normal Range

37-42 weeks considered normal, with 39-40 weeks being optimal for delivery.

Due Date Calculation Methods

Several methods exist for calculating your estimated due date, each with different levels of accuracy depending on your specific situation. The most appropriate method depends on factors like cycle regularity, conception awareness, and access to early ultrasound. Understanding these different approaches helps you and your healthcare provider determine the most reliable due date for your pregnancy. Explore how various factors affect accuracy and learn about important prenatal appointments.

  • Last Menstrual Period (LMP): Most common method using Naegele's Rule, adding 280 days to the first day of your last period. Works best with regular 28-day cycles.

  • Ultrasound Dating: Most accurate in first trimester (6-13 weeks), measuring crown-rump length. Can date pregnancy within 3-5 days when performed early.

  • Conception Date: If known precisely (IVF, tracking ovulation), add 266 days. Eliminates cycle variation but requires exact conception timing.

  • IVF Transfer Date: Most precise method. Add 261 days for 5-day blastocyst or 263 days for 3-day embryo transfer.

  • Cycle Adjustment: For cycles different from 28 days, adjust the LMP calculation by the difference (e.g., 35-day cycle adds 7 days).

💡 Method Accuracy Comparison

±3-5 days
First Trimester Ultrasound - Most accurate dating method
±7-10 days
Regular Cycle LMP - Good accuracy with known dates
±2-3 days
IVF Transfer - Most precise with known timing

Your Pregnancy Timeline

Pregnancy unfolds over approximately 40 weeks, with each phase bringing unique developments and milestones. Understanding this timeline helps you prepare for changes, schedule important appointments, and track your baby's growth. The journey from conception to birth involves remarkable transformations for both mother and baby, with specific weeks marking critical developmental achievements. Learn about trimester divisions and discover key pregnancy milestones. Understanding your timeline also helps with preparation planning.

🌱 Early Pregnancy (Weeks 1-12)

Weeks 1-4:
  • Conception and implantation occur
  • Missed period signals pregnancy
  • Positive pregnancy test possible
  • Early symptoms may begin
Weeks 5-8:
  • Heart begins beating (week 6)
  • Major organs start forming
  • First prenatal appointment
  • Morning sickness common
Weeks 9-12:
  • Fetus fully formed
  • NIPT screening available
  • Nuchal translucency scan
  • Risk of miscarriage decreases

👶 Mid to Late Pregnancy (Weeks 13-40)

Weeks 13-20:
  • Second trimester begins
  • Gender determination possible
  • Anatomy scan at 18-20 weeks
  • First movements felt
Weeks 21-30:
  • Viability milestone (24 weeks)
  • Regular movement patterns
  • Glucose screening (28 weeks)
  • Third trimester begins
Weeks 31-40:
  • Rapid weight gain phase
  • Baby drops into position
  • Full term at 37 weeks
  • Labor signs begin

🗓️ Term Classifications

Preterm
Before 37 weeks
Early Term
37-38 weeks
Full Term
39-40 weeks
Late/Post Term
41+ weeks

Understanding Pregnancy Trimesters

Pregnancy is divided into three trimesters, each lasting approximately 13-14 weeks and characterized by distinct developmental stages and maternal changes. Understanding these phases helps you anticipate physical and emotional changes, prepare for specific challenges, and celebrate important milestones. Each trimester brings unique experiences, from early pregnancy symptoms to preparing for delivery. Learn about specific milestones within each trimester and discover essential prenatal care for each phase.

🤰 Trimester Overview

First Trimester
Weeks 1-13
Organ development, highest miscarriage risk, morning sickness common
Second Trimester
Weeks 14-27
"Golden period" with increased energy, visible bump, fetal movement
Third Trimester
Weeks 28-40
Rapid growth, birth preparation, increased discomfort, nesting

First Trimester (Weeks 1-13)

The first trimester is a critical period of rapid development when all major organs and systems form. Despite minimal external changes, profound transformations occur internally. Common experiences include fatigue, morning sickness, breast tenderness, and emotional fluctuations due to hormonal changes. This period carries the highest miscarriage risk, making early prenatal care essential. Key developments include heart formation (week 6), limb development (week 8), and completion of major organ formation (week 10). Compare with second trimester and third trimester experiences.

Physical Changes

  • • Morning sickness and nausea
  • • Extreme fatigue
  • • Breast tenderness and growth
  • • Frequent urination
  • • Food aversions or cravings

Baby Development

  • • Neural tube forms (spine and brain)
  • • Heart begins beating
  • • Major organs develop
  • • Limbs and fingers form
  • • Size: poppy seed to lime

Second Trimester (Weeks 14-27)

Often called the "golden period" of pregnancy, the second trimester typically brings relief from early pregnancy symptoms and renewed energy. The risk of miscarriage drops significantly, and many couples feel comfortable announcing their pregnancy. You'll experience exciting milestones like feeling first movements (quickening) around weeks 16-20 and learning baby's sex at the anatomy scan. Physical changes become more apparent with a visible baby bump, while baby develops hearing, fingerprints, and regular sleep-wake cycles.

Third Trimester (Weeks 28-40)

The final trimester focuses on growth and birth preparation. Baby gains most of their birth weight during this period, while you may experience increased discomfort from the growing uterus. Common experiences include back pain, swelling, Braxton Hicks contractions, and difficulty sleeping. Important milestones include the viability point continuation, lung maturation, and baby dropping into birth position. Regular monitoring increases with more frequent prenatal visits, kick counts, and preparation for delivery signs.

Key Pregnancy Milestones

Throughout your pregnancy journey, specific weeks mark critical developmental achievements and important medical checkpoints. Understanding these milestones helps you track progress, prepare for appointments, and celebrate your baby's growth. Each milestone represents significant development that healthcare providers monitor to ensure healthy progression. These markers also guide decisions about prenatal testing, interventions if needed, and delivery planning. Learn how these connect with essential prenatal care and preparation strategies.

🌟 Early Milestones

  • Week 4: Missed period, positive test
  • Week 6: Heart starts beating
  • Week 8: First prenatal visit
  • Week 10: NIPT screening available
  • Week 12: End of first trimester

🎯 Mid Milestones

  • Week 16: Gender determination
  • Week 18-20: Anatomy scan
  • Week 20: Halfway point
  • Week 24: Viability milestone
  • Week 28: Third trimester begins

🎊 Final Milestones

  • Week 32: Baby shower time
  • Week 36: Weekly appointments
  • Week 37: Early term begins
  • Week 39: Full term reached
  • Week 40: Due date arrives

Factors Affecting Due Date Accuracy

Several factors influence the accuracy of due date calculations, making some estimates more reliable than others. Understanding these variables helps set realistic expectations and explains why your due date might change during pregnancy. Healthcare providers consider multiple factors when determining your most accurate due date, sometimes adjusting initial estimates based on ultrasound findings or other clinical indicators. Recognizing these influences helps you understand why friends' experiences may differ from yours and why flexibility in birth planning is important.

✅ Increases Accuracy

• Regular cycles: Consistent 28-day cycles
• Known LMP: Certain of last period date
• Early ultrasound: Dating scan before 13 weeks
• IVF pregnancy: Known conception timing
• Ovulation tracking: Confirmed ovulation date

❌ Decreases Accuracy

• Irregular cycles: Variable or long cycles
• Uncertain dates: Unsure of last period
• Late ultrasound: Dating after 20 weeks
• PCOS: Affects cycle regularity
• Recent contraception: Post-pill cycles vary

Essential Prenatal Appointments

Regular prenatal care is crucial for monitoring your health and your baby's development throughout pregnancy. These appointments allow healthcare providers to track progress, identify potential concerns early, and provide necessary interventions. The frequency and types of appointments vary by trimester and individual risk factors. Understanding the typical schedule helps you plan and prepare questions for your provider. Each visit serves specific purposes in ensuring a healthy pregnancy and preparing for delivery.

📋 Typical Appointment Schedule

🗓️
Weeks 4-28: Monthly visits for routine monitoring
📅
Weeks 28-36: Biweekly visits with increased monitoring
📆
Weeks 36-40: Weekly visits until delivery
🏥
Post 40 weeks: Twice weekly with additional testing

Preparing for Your Due Date

Preparation for your baby's arrival involves practical planning, emotional readiness, and understanding that babies rarely arrive exactly on schedule. Starting preparations early, typically in the second trimester, helps reduce stress as your due date approaches. Consider creating flexible plans that accommodate early or late arrival, and focus on essentials first. Remember that being "ready" is more about being prepared for various scenarios than having everything perfect.

👶 Baby Essentials

• Nursery: Crib, changing table, basics
• Clothing: Newborn and 0-3 month sizes
• Feeding: Breast/bottle supplies ready
• Diapers: Stock newborn and size 1
• Car seat: Installed and inspected

🏥 Hospital Planning

• Hospital bag: Packed by week 36
• Birth plan: Discussed with provider
• Route planned: Know multiple routes
• Paperwork: Pre-registration complete
• Support team: Contact list ready

🏠 Home Preparation

• Deep clean: Complete by week 35
• Meal prep: Freezer meals ready
• Help arranged: Postpartum support
• Pets: Care plans in place
• Work leave: Arrangements finalized

Common Due Date Questions

Understanding due dates raises many questions for expectant parents. From accuracy concerns to what happens if you go past your due date, having clear information helps reduce anxiety and supports informed decision-making. These common concerns reflect the experiences of many parents navigating pregnancy timing and planning.

❓ Timing Questions

• "Is it normal to go past due date?"
Yes, especially for first pregnancies. 50% deliver after their due date.
• "Can stress affect delivery timing?"
Extreme stress may influence timing, but normal stress doesn't significantly impact due dates.
• "Why do first babies often come late?"
The body needs time to prepare for first labor; subsequent pregnancies often progress faster.

✅ Planning Questions

• "When should I stop working?"
Varies by individual; many work until labor begins, others stop at 36-38 weeks.
• "Can I choose my delivery date?"
Elective induction typically not before 39 weeks unless medically indicated.
• "Should I plan events near my due date?"
Best to keep plans flexible from 37 weeks onward.

Signs Labor is Approaching

As your due date nears, your body provides various signals that labor is approaching. These signs can occur weeks, days, or hours before labor begins, and experiences vary significantly among women. Some may experience many pre-labor signs while others have few warnings before active labor starts. Understanding these signals helps you prepare mentally and practically for your baby's arrival, though predicting exact timing remains impossible.

Early signs include the baby "dropping" lower into the pelvis (lightening), increased Braxton Hicks contractions, cervical changes your provider may note, loss of the mucus plug, and nesting instincts. More imminent signs include regular, intensifying contractions, water breaking, bloody show, and back pain that doesn't ease with position changes. Remember that labor progression is unique to each person and pregnancy - trust your instincts and contact your healthcare provider when you're uncertain.

Key Takeaways for Due Date Calculation

Due dates are estimates with only 5% of babies arriving exactly on their calculated date. The normal delivery window spans from 37 to 42 weeks, with 90% of babies arriving within two weeks of their due date. Use our calculator to explore different calculation methods including LMP, ultrasound, conception date, and IVF transfer for the most accurate estimate based on your situation.

First-trimester ultrasounds provide the most accurate dating (within 3-5 days), while LMP calculations work well for regular cycles. Factors like cycle length, PCOS, and recent contraception use affect accuracy. Understanding accuracy factors helps set realistic expectations and explains why due dates might be adjusted during pregnancy.

Pregnancy unfolds through three distinct trimesters, each bringing unique developments and challenges. Track key milestones like viability at 24 weeks, full term at 37 weeks, and optimal delivery at 39-40 weeks. Regular prenatal appointments monitor progress and ensure healthy development throughout your journey.

Preparation should begin early in pregnancy with flexible planning that accommodates early or late arrival. Focus on essentials by 36 weeks including hospital bag, nursery basics, and support arrangements. Remember that being "ready" means being prepared for various scenarios rather than having everything perfect. Use our Pregnancy Weight Gain Calculator and other tools to track your pregnancy health.

Frequently Asked Questions

Due date calculations provide an estimate, with only about 5% of babies born on their exact due date. Most babies (90%) arrive within two weeks before or after the estimated date. First-trimester ultrasounds are typically most accurate (within 3-5 days), while LMP calculations can vary by up to two weeks depending on cycle regularity.
Naegele's Rule is the most common method for calculating due dates, adding 280 days (40 weeks) to the first day of your last menstrual period (LMP). The formula assumes a 28-day cycle with ovulation on day 14. For different cycle lengths, the calculation adjusts accordingly - longer cycles push the due date later, shorter cycles earlier.
Ultrasound dates may differ from LMP calculations due to irregular cycles, uncertain LMP dates, or individual growth variations. Early pregnancy ultrasounds (6-13 weeks) measure crown-rump length and are most accurate. If the difference exceeds 7 days in the first trimester, doctors typically use the ultrasound date as it's more reliable.
IVF due dates are calculated based on the embryo transfer date and embryo age. For a 3-day embryo transfer, add 263 days to the transfer date. For a 5-day blastocyst transfer, add 261 days. IVF calculations are often most precise since the exact conception timing is known, eliminating cycle variation uncertainties.
Pregnancy is divided into three trimesters: First trimester (weeks 1-13) involves major organ development and highest miscarriage risk. Second trimester (weeks 14-27) often brings increased energy and fetal movement. Third trimester (weeks 28-40) involves rapid growth and preparation for birth. Each trimester has distinct developmental milestones and maternal changes.
Babies are considered: Early term at 37-38 weeks (fully developed but may benefit from more time), Full term at 39-40 weeks (optimal delivery time with lowest risks), Late term at 41 weeks, and Post-term after 42 weeks. Medical professionals now encourage waiting until at least 39 weeks for elective deliveries unless medically indicated.
Pregnancy weeks are counted from the first day of your last menstrual period (LMP), not from conception. This means you're considered 'pregnant' for about two weeks before conception actually occurs. At conception, you're already considered 2 weeks pregnant. A full-term pregnancy is 40 weeks from LMP or 38 weeks from conception.
If you're unsure of your LMP, an early ultrasound (ideally before 13 weeks) can accurately date your pregnancy. The ultrasound measures the baby's size and compares it to standard growth charts. Other indicators like conception date (if known), pregnancy symptoms onset, or first positive pregnancy test can provide rough estimates until an ultrasound confirms dating.
Cycle length significantly impacts due date calculations. The standard 280-day calculation assumes a 28-day cycle with ovulation on day 14. For a 35-day cycle, ovulation typically occurs around day 21, so add 7 days to the standard due date. For a 21-day cycle, ovulation is around day 7, so subtract 7 days. Our calculator automatically adjusts for your specific cycle length.
Key pregnancy milestones include: Week 6-8 (heartbeat detectable), Week 10-13 (NIPT screening available), Week 11-14 (nuchal translucency scan), Week 18-22 (anatomy scan), Week 24 (viability milestone), Week 28 (glucose screening), Week 36 (Group B strep test), and Week 37+ (baby considered term). Regular prenatal appointments help monitor these milestones and ensure healthy development.

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