👶Due Date Calculator
Calculate your pregnancy due date based on last menstrual period or conception date
Last updated: November 7, 2025
Welcome to our free due date calculator, also known as a pregnancy due date calculator or pregnancy calculator. This specialized due date calculator is designed to help you calculate due date and estimate your pregnancy due date accurately. Our pregnancy due date calculator uses Naegele's rule calculator methodology to provide your estimated due date (EDD) based on your last menstrual period or conception date.
Understanding how to calculate due date is essential for expecting mothers and healthcare providers. This pregnancy due date estimation tool helps you estimate baby's birth date and understand your pregnancy length in weeks. Our due date predictor also functions as a gestational age calculator and pregnancy trimester calculator, providing comprehensive information about your pregnancy timeline.
Our due date calculator provides not just your estimated due date, but also your current week of pregnancy, days until due date, and current trimester. This conception date calculator and last menstrual period (LMP) calculator gives you a complete understanding of your pregnancy timeline, making it easier to plan and prepare for your baby's arrival.
What is a due date? Understanding estimated due date (EDD)
A pregnancy due date, also known as an estimated due date (EDD), is the calculated date when your baby is expected to be born. The due date calculator uses mathematical formulas to estimate this date based on when pregnancy began. Understanding how to calculate due date helps you prepare for your baby's arrival and schedule important pregnancy prenatal appointment visits.
It's important to understand the difference between due date and due month. While the calculator provides a specific date, only about 5% of babies are born on their exact due date. Most babies are born within two weeks before or after the estimated due date. This is why due month calculation is also important for planning purposes.
The pregnancy due date estimation is based on the average pregnancy length in weeks, which is approximately 40 weeks (280 days) from the first day of your last menstrual period, or 38 weeks (266 days) from conception. This gestational age calculator helps track your pregnancy progress and plan for important milestones.
How to calculate my baby's due date using Naegele's rule
How to calculate my baby's due date using Naegele's rule is the most common method for pregnancy due date estimation. Our Naegele's rule calculator applies this standard medical formula, which was developed by German obstetrician Franz Naegele in the early 19th century.
Naegele's Rule Formula:
Due Date = First Day of LMP + 1 year - 3 months + 7 days
Or simplified: Due Date = LMP + 280 days (40 weeks)
This due date calculator method works by:
- Taking the first day of your last menstrual period (LMP)
- Adding one year to that date
- Subtracting three months
- Adding seven days
Example: Calculate due date from LMP
LMP: January 15, 2024
Step 1: Add 1 year: January 15, 2025
Step 2: Subtract 3 months: October 15, 2024
Step 3: Add 7 days: October 22, 2024
Estimated Due Date: October 22, 2024
This Naegele's rule calculator method assumes a 28-day menstrual cycle with ovulation occurring on day 14. If your pregnancy cycle length varies, you can adjust the calculation. How to calculate due date if cycle length varies involves adjusting for your specific cycle length, which our calculator handles automatically when you enter your average cycle length.
How to estimate pregnancy due date from last menstrual period
How to estimate pregnancy due date from last menstrual period is the most common method used by healthcare providers. Our last menstrual period (LMP) calculator uses this method to provide accurate due date estimates. This approach is reliable because the first day of your last menstrual period is usually easier to remember than the exact conception date.
Steps to Calculate from LMP
- Identify the first day of your last menstrual period
- Add 280 days (40 weeks) to that date
- Alternatively, add 1 year, subtract 3 months, and add 7 days
- The result is your estimated due date
Why LMP is Used
The last menstrual period (LMP) calculator method is preferred because most women can recall when their last period started more accurately than when conception occurred. This makes it the standard method for pregnancy due date estimation in medical practice.
How to calculate length of pregnancy in weeks from LMP involves counting the weeks from the first day of your LMP. Our calculator automatically performs this calculation, showing you exactly how many weeks and days you are into your pregnancy.
When is my due date based on conception date
When is my due date based on conception date is another method for calculating your due date. Our conception date calculator uses this approach when you know the exact date of conception. This method is particularly useful if you've been tracking ovulation or used assisted reproductive technologies.
Conception Date Formula:
Due Date = Conception Date + 266 days (38 weeks)
This is based on the typical gestation period from conception to birth.
How does conception date affect pregnancy length? The calculation from conception date accounts for the actual fertilization date, which provides a more precise estimate in some cases. However, calculate conception date can be challenging since most women don't know the exact moment of conception, which is why the LMP method is more commonly used.
When to Use Conception Date
Use the conception date calculator method when you know the exact date of conception, such as after IVF treatment, when using ovulation tracking methods, or when you have precise information about when fertilization occurred.
Comparison with LMP Method
The conception date method typically gives a due date that is about 2 weeks earlier than the LMP method, since conception usually occurs about 2 weeks after the start of the last menstrual period.
What is gestational age and how is it calculated
What is gestational age and how is it calculated? Gestational age is the age of the pregnancy measured from the first day of the last menstrual period. Our gestational age calculator helps you understand how far along you are in your pregnancy. This is different from fetal age, which is measured from the actual date of conception.
Gestational Age vs Fetal Age
Gestational age is typically 2 weeks more than fetal age because it includes the two weeks before conception when the body is preparing for pregnancy. For example, if you're 10 weeks pregnant by gestational age, the fetus is actually 8 weeks old.
How Gestational Age is Calculated
Our gestational age calculator calculates gestational age by counting the number of weeks and days from the first day of your last menstrual period to the current date. This is the standard method used by healthcare providers worldwide.
Why Gestational Age Matters
Gestational age is important for tracking fetal development, scheduling prenatal tests, determining due dates, and identifying any potential issues. It's also used to assess premature birth risk factors and plan appropriate medical care.
Pregnancy trimester timeline and symptoms: Pregnancy trimesters explained
Our pregnancy trimester calculator helps you understand which trimester you're in. Pregnancy trimesters explained divides pregnancy into three main phases, each lasting approximately 13-14 weeks. Understanding the pregnancy trimester timeline and symptoms helps you know what to expect during each stage of pregnancy.
First Trimester (Weeks 1-13)
The first trimester is a critical period of development. Common experiences include:
- Morning sickness and nausea
- Fatigue and exhaustion
- Breast tenderness
- Frequent urination
- Early pregnancy prenatal appointment visits
- Blood test for hCG level to confirm pregnancy
Second Trimester (Weeks 14-26)
Often called the "honeymoon period" of pregnancy:
- Increased energy levels
- Baby's movements become noticeable
- Anatomy scan ultrasound
- Fundal height measurement begins
- Doppler ultrasonography in pregnancy for monitoring
Third Trimester (Weeks 27-40)
The final stretch before delivery:
- Increased discomfort and weight
- Braxton Hicks contractions
- More frequent pregnancy prenatal appointment visits
- Preparation for labor and delivery
- Monitoring for premature birth risk factors
Our pregnancy trimester calculator automatically determines which trimester you're in based on your current week of pregnancy. This helps you understand pregnancy trimesters explained in the context of your specific pregnancy timeline and plan for what prenatal tests are required each trimester.
What affects the accuracy of estimated due date
Understanding what affects the accuracy of estimated due date is important for managing expectations. While our due date calculator provides an estimate, several factors can influence the actual delivery date.
Factors Affecting Due Date Accuracy
- Pregnancy cycle length: Women with irregular cycles may have less accurate estimates
- Ovulation timing: Early or late ovulation affects the calculation
- Ultrasound measurements: Early ultrasounds (before 13 weeks) provide the most accurate dating
- Multiple pregnancies: Twins or multiples may have different due dates
- Medical history: Previous pregnancies and medical conditions can affect timing
Pregnancy Ultrasound Due Date
A pregnancy ultrasound due date can be more accurate than LMP-based calculations, especially when performed early in pregnancy (8-13 weeks). Ultrasounds measure fetal size and development to estimate gestational age and due date. Your healthcare provider may adjust your due date based on pregnancy ultrasound due date measurements if they differ significantly from the LMP calculation.
How to Calculate Due Date if Cycle Length Varies
How to calculate due date if cycle length varies requires adjusting the standard calculation. Our calculator allows you to enter your average cycle length, which adjusts the ovulation timing and provides a more accurate estimate for women with cycles that are not exactly 28 days.
How many weeks is a normal pregnancy: Pregnancy length in weeks
Understanding how many weeks is a normal pregnancy and pregnancy length in weeks helps you know what to expect. A full-term pregnancy typically lasts 40 weeks from the first day of the last menstrual period, which equals 280 days or approximately 9 months.
Pregnancy Length Categories
- Preterm: Born before 37 weeks (associated with premature birth risk factors)
- Early term: Born between 37-38 weeks
- Full term: Born between 39-40 weeks (ideal timing)
- Late term: Born between 41-41 weeks
- Post-term: Born after 42 weeks
Normal Pregnancy Length
A pregnancy length in weeks of 37-42 weeks is considered normal. Most babies are born between 38-42 weeks, with the average being around 40 weeks. Our pregnancy calculator calculates based on the standard 40-week (280-day) pregnancy length from LMP.
Risk factors for premature birth during pregnancy
Understanding risk factors for premature birth during pregnancy is important for expectant mothers. Premature birth occurs when a baby is born before 37 weeks of pregnancy. Our due date calculator helps you track your pregnancy progress and identify when you might be at risk.
Common Risk Factors
- Previous premature birth
- Multiple pregnancies (twins, triplets)
- Certain medical conditions (diabetes, high blood pressure)
- Infections during pregnancy
- Smoking, alcohol, or drug use
- Stress and lifestyle factors
- Short time between pregnancies
Prevention and Monitoring
Regular pregnancy prenatal appointment visits help monitor for premature birth risk factors. Your healthcare provider will check for signs of preterm labor and provide guidance on reducing risks. Understanding your due date helps you track your progress and identify any concerns early.
What prenatal tests are required each trimester: Pregnancy prenatal appointment
Understanding what prenatal tests are required each trimester helps you prepare for your pregnancy prenatal appointment visits. Regular prenatal care is essential for monitoring your health and your baby's development throughout pregnancy.
First Trimester Tests
- Blood test for hCG level to confirm pregnancy
- Blood type and Rh factor testing
- Genetic screening tests
- Chorionic villus sampling (CVS) if needed
- Dating ultrasound for accurate due date
Second Trimester Tests
- Anatomy scan ultrasound (18-22 weeks)
- Quad screen or integrated screening
- Glucose tolerance test for gestational diabetes
- Fundal height measurement begins
- Doppler ultrasonography in pregnancy for fetal monitoring
Third Trimester Tests
- Group B streptococcus (GBS) screening
- Non-stress test (NST) if needed
- Biophysical profile if concerns arise
- More frequent fundal height measurement
- Monitoring for premature birth risk factors
Regular pregnancy prenatal appointment visits allow your healthcare provider to monitor your pregnancy progress, adjust your due date if needed based on pregnancy ultrasound due date measurements, and ensure both you and your baby are healthy throughout the pregnancy.
How to interpret hCG levels during pregnancy: Blood test for hCG level
Understanding how to interpret hCG levels during pregnancy is important for early pregnancy monitoring. A blood test for hCG level measures the human chorionic gonadotropin hormone, which is produced by the placenta after implantation.
What is hCG?
hCG (human chorionic gonadotropin) is a hormone that doubles approximately every 48-72 hours in early pregnancy. A blood test for hCG level is one of the first tests performed to confirm pregnancy and estimate how far along you are.
Normal hCG Levels by Week
- 3 weeks: 5-50 mIU/mL
- 4 weeks: 5-426 mIU/mL
- 5 weeks: 18-7,340 mIU/mL
- 6 weeks: 1,080-56,500 mIU/mL
- 7-8 weeks: 7,650-229,000 mIU/mL
Interpreting hCG Levels
How to interpret hCG levels during pregnancy involves understanding that levels should roughly double every 48-72 hours in early pregnancy. Abnormal levels or patterns may indicate issues such as ectopic pregnancy, miscarriage risk, or miscalculated due dates. Your healthcare provider will interpret your blood test for hCG level results in the context of your pregnancy due date estimation.
Pregnancy monitoring: Fundal height measurement and Doppler ultrasonography
During your pregnancy prenatal appointment visits, your healthcare provider uses various methods to monitor your pregnancy progress. Fundal height measurement and Doppler ultrasonography in pregnancy are important tools for tracking fetal development and verifying due date accuracy.
Fundal Height Measurement
Fundal height measurement involves measuring the distance from the pubic bone to the top of the uterus. This measurement in centimeters should approximately match the number of weeks pregnant you are. For example, at 24 weeks, the fundal height should be around 24 cm. This measurement helps verify that your baby is growing appropriately and can help confirm your pregnancy due date estimation.
Doppler Ultrasonography in Pregnancy
Doppler ultrasonography in pregnancy uses sound waves to monitor blood flow in the baby's vessels and the placenta. This non-invasive test helps assess fetal well-being, especially in the second and third trimesters. It's often used alongside pregnancy ultrasound due date measurements to ensure accurate dating and monitor for any complications.
How to use a pregnancy calculator to find due date
How to use a pregnancy calculator to find due date is straightforward with our tool. Our pregnancy calculator provides an easy way to calculate due date and get comprehensive information about your pregnancy timeline.
Steps to Use the Calculator
- Select your calculation method (LMP or Conception Date)
- Enter the date (first day of LMP or conception date)
- Enter your average cycle length (if using LMP method)
- Click calculate to get your results
What You'll Get
- Estimated due date (EDD)
- Current week of pregnancy
- Days until due date
- Current trimester
- Pregnancy milestones information
Our due date calculator and pregnancy milestones calculator work together to provide you with a complete picture of your pregnancy timeline. This helps you plan for important events, schedule pregnancy prenatal appointment visits, and prepare for your baby's arrival.
Special considerations and important notes
Understanding the Difference Between Due Date and Due Month
Understanding the difference between due date and due month is important for realistic expectations. While the calculator provides a specific date, it's more accurate to think in terms of a due month or due window. Most babies are born within two weeks before or after the estimated due date, so planning for a due month rather than a specific date is more practical.
Due Date Adjustments
Your healthcare provider may adjust your due date based on pregnancy ultrasound due date measurements, especially if done early in pregnancy (before 13 weeks). Early ultrasounds provide the most accurate dating because fetal development is more standardized in the first trimester. Later ultrasounds may be less reliable for dating purposes.
Irregular Cycles
If you have irregular menstrual cycles, the standard due date calculator may be less accurate. In these cases, how to calculate due date if cycle length varies becomes important. Our calculator allows you to adjust for your specific cycle length, and your healthcare provider may rely more heavily on early ultrasound dating.
Multiple Pregnancies
For twins or multiple pregnancies, the due date calculation remains the same, but delivery often occurs earlier. Understanding premature birth risk factors is especially important for multiple pregnancies, as they are more likely to deliver before the estimated due date.
Frequently Asked Questions
The due date calculator provides an estimate based on average pregnancy length (280 days from LMP). Only about 5% of babies are born on their exact due date. Most are born within 2 weeks before or after. The accuracy depends on factors like cycle regularity, ovulation timing, and if early ultrasound dating is used.
If you have irregular periods, the LMP method may not be as accurate. An early ultrasound (between 8-13 weeks) provides the most accurate due date estimate. You can also adjust for your average cycle length in the calculator to improve accuracy.
Your healthcare provider may adjust your due date based on ultrasound measurements, especially if done early in pregnancy (before 13 weeks). Early ultrasounds provide the most accurate dating because fetal development is more standardized in the first trimester.
To calculate due date from LMP, add 280 days (40 weeks) to the first day of your last menstrual period. Alternatively, add 1 year, subtract 3 months, and add 7 days. This is known as Naegele's rule, which our calculator uses automatically.
Naegele's rule is a standard method for calculating due dates. It assumes a 28-day menstrual cycle with ovulation on day 14. The formula is: Due Date = LMP + 1 year - 3 months + 7 days, or simplified as LMP + 280 days.
To calculate due date from conception date, add 266 days (38 weeks) to the conception date. This method is useful when you know the exact date of conception, such as after IVF or when tracking ovulation.
Gestational age is the age of the pregnancy measured from the first day of the last menstrual period. It's typically 2 weeks more than fetal age (which is measured from conception) because it includes the two weeks before conception when the body prepares for pregnancy.
A normal pregnancy lasts 37-42 weeks from the first day of the last menstrual period. Full-term is considered 39-40 weeks, with most babies born between 38-42 weeks. Our calculator uses the standard 40-week (280-day) pregnancy length.
Pregnancy is divided into three trimesters: First trimester (weeks 1-13), second trimester (weeks 14-26), and third trimester (weeks 27-40). Each trimester has different symptoms, milestones, and prenatal test requirements. Our calculator automatically determines which trimester you're in.
Factors affecting due date accuracy include cycle length regularity, ovulation timing, ultrasound measurements (especially early ultrasounds before 13 weeks), multiple pregnancies, and medical history. Early ultrasounds provide the most accurate dating.
If your cycle length varies, you can enter your average cycle length in the calculator. The calculator adjusts the ovulation timing based on your cycle length, providing a more accurate estimate. For irregular cycles, early ultrasound dating is often more reliable.
The due date is a specific calculated date, while the due month refers to the expected month of delivery. Since only about 5% of babies are born on their exact due date, it's more practical to think in terms of a due month or due window (typically 2 weeks before or after the due date).
First trimester: hCG blood test, blood type, genetic screening, dating ultrasound. Second trimester: anatomy scan, quad screen, glucose tolerance test, fundal height measurements, Doppler ultrasound. Third trimester: GBS screening, non-stress tests, more frequent fundal height measurements, monitoring for premature birth risk factors.
hCG (human chorionic gonadotropin) is a hormone produced by the placenta after implantation. Blood tests measure hCG levels to confirm pregnancy and estimate how far along you are. Levels typically double every 48-72 hours in early pregnancy.
Fundal height measurement measures the distance from the pubic bone to the top of the uterus in centimeters. It should approximately match the number of weeks pregnant you are (e.g., 24 cm at 24 weeks). It helps verify baby's growth and confirm due date accuracy.
Doppler ultrasonography uses sound waves to monitor blood flow in the baby's vessels and placenta. It's a non-invasive test used in the second and third trimesters to assess fetal well-being and is often used alongside ultrasound dating measurements.
Risk factors include previous premature birth, multiple pregnancies, certain medical conditions (diabetes, high blood pressure), infections during pregnancy, smoking/alcohol/drug use, stress, and short time between pregnancies. Regular prenatal appointments help monitor these risks.