Pregnancy dating and due date tool
Pregnancy Calculator and Due Date Calculator
A pregnancy calculator helps estimate how far along you are and when your baby may be due. By entering the first day of your last menstrual period, or LMP, and your average menstrual cycle length, the calculator can estimate your current pregnancy week, pregnancy month, gestational age and estimated date of delivery, or EDD.
Pregnancy is usually dated from the first day of the last menstrual period rather than the exact date of conception. This means the same tool can function as an LMP calculator, EDD calculator, pregnancy week calculator by LMP and gestational age calculator. The result provides an initial pregnancy timeline, while your doctor may confirm or refine the dates using your menstrual history, IVF treatment dates or an early ultrasound.
Calculator results are estimates and do not replace medical dating or ultrasound assessment when recommended.
Your estimated pregnancy timeline
Your Pregnancy Calculator Result
Your due date and pregnancy timeline are estimates. Your doctor may confirm or refine pregnancy dating using clinical information or ultrasound findings.
Motherhood Hospitals
Plan Your Pregnancy Milestones with Motherhood Hospitals
Your estimated pregnancy week and due date can help you understand the broader pregnancy timeline. For personalised guidance about antenatal consultations, pregnancy scans or maternity care, connect with the Motherhood Hospitals team.
Pregnancy week tracking
Pregnancy Week Calculator
A pregnancy calculator week by week helps you understand your current stage of pregnancy and how many weeks may remain before your estimated due date.
Pregnancy is commonly measured in weeks because fetal development and antenatal care milestones are easier to monitor this way. A full-term pregnancy is approximately 40 weeks when counted from the first day of the last menstrual period.
Your pregnancy week calculator by LMP result can help you understand:
- Your estimated pregnancy week
- Your approximate pregnancy month
- Your current trimester
- Your estimated delivery date
- How many weeks may remain until your due date
Due date estimate
Calculate My Due Date
Enter the first day of your last menstrual period and your average menstrual cycle length into the calculator. The tool will estimate your pregnancy week and expected due date based on the information you provide.
Your calculator result is an estimate and should not replace medical dating or an ultrasound assessment when your doctor recommends one.
How the estimate works
How Does the Pregnancy Due Date Calculator Work?
A pregnancy due date calculator estimates your expected delivery date by using the first day of your last menstrual period as the starting point of pregnancy.
For a regular menstrual cycle, the calculation generally assumes a pregnancy duration of about 280 days, or 40 weeks, from the first day of the last period. A pregnancy due calculator may also consider cycle length when estimating the timeline.
The calculated date is an estimated due date rather than a guaranteed delivery date. Many babies are born before or after their estimated due date.
Weeks and months
Understand Your Pregnancy Week and Month
A pregnancy week calculator estimates how many completed weeks of pregnancy have passed from the first day of your last menstrual period.
Pregnancy is generally counted as approximately 40 weeks. Months are less precise because calendar months do not contain an equal number of weeks. This is why healthcare professionals usually describe pregnancy in weeks and days rather than only months.
A pregnancy month calculator or pregnancy month calculator by week can still help you understand your approximate pregnancy month.
| Pregnancy Month | Approximate Pregnancy Weeks |
|---|---|
| Month 1 | Weeks 1 to 4 |
| Month 2 | Weeks 5 to 8 |
| Month 3 | Weeks 9 to 13 |
| Month 4 | Weeks 14 to 17 |
| Month 5 | Weeks 18 to 22 |
| Month 6 | Weeks 23 to 27 |
| Month 7 | Weeks 28 to 31 |
| Month 8 | Weeks 32 to 35 |
| Month 9 | Weeks 36 to 40 |
The exact conversion between pregnancy weeks and months is approximate. Your pregnancy week remains the more precise way to monitor gestational progress.
Pregnancy dating methods
LMP, EDD and Pregnancy Week Calculator: How Your Pregnancy Dates Are Calculated
Your pregnancy can be dated using different information depending on what is known. For many naturally conceived pregnancies, the first day of the last menstrual period is used to estimate both gestational age and the estimated date of delivery (EDD). An LMP calculator, LMP EDD calculator or pregnancy week calculator by LMP applies this same principle automatically. Your doctor may also consider conception timing, IVF transfer dates or early ultrasound findings when confirming your pregnancy timeline.
Doctors commonly use:
- The first day of your last menstrual period
- Your estimated conception date
- An IVF transfer date when applicable
- An ultrasound scan, especially in early pregnancy
A due date calculator provides an initial estimate, while your doctor considers clinical information when confirming your pregnancy dates.
Last Menstrual Period
The LMP, or last menstrual period, is the first day of your most recent menstrual period and is one of the standard starting points used for pregnancy dating.
Pregnancy is counted from the first day of the LMP even though conception usually happens later. For someone with a regular 28-day menstrual cycle, the estimated due date is commonly calculated at approximately 280 days, or 40 weeks, from the first day of the last period.
An LMP calculator, LMP EDD calculator, pregnancy week calculator by LMP or gestational age calculator uses this date to estimate how many weeks pregnant you are and your expected delivery date.
LMP-based dating works best when:
- You remember the first day of your last period
- Your menstrual cycles are reasonably regular
- Your cycle length does not vary significantly from month to month
If your periods are irregular, your LMP is uncertain, or your cycle length varies considerably, the calculated date may be less accurate. In such cases, your doctor may use an early pregnancy ultrasound to help confirm gestational age and the estimated due date.
Conception Date
Conception generally occurs around the time an egg is fertilised by sperm. However, determining the exact conception date in a naturally conceived pregnancy can be difficult because sperm can survive in the reproductive tract for several days.
A pregnancy date calculator may estimate conception based on the menstrual cycle or estimated due date, but the result should not be treated as the exact date conception occurred.
Knowing the likely conception window can help provide context, but doctors usually use gestational age rather than conception age for routine pregnancy care.
IVF Transfer Date
Pregnancy dating after IVF can be more precise because the timing of fertilisation and embryo transfer is known.
An IVF due date calculator or pregnancy week calculator IVF uses the embryo transfer date and embryo age to estimate gestational age and expected delivery date.
An IVF pregnancy calculator therefore follows a different calculation method from a standard LMP-based calculator. Your fertility specialist can confirm the dating method appropriate for your treatment cycle.
Ultrasound Scan
Ultrasound can help estimate gestational age by measuring the developing pregnancy.
An early pregnancy scan, particularly during the first trimester, can provide useful information when:
- The last menstrual period date is uncertain
- Menstrual cycles are irregular
- The calculated dates do not match the ultrasound findings
- There is uncertainty about gestational age
Your doctor may compare the ultrasound result with your LMP-based estimate before confirming your expected due date.
LMP vs Ultrasound Due Date: Why the Dates May Be Different
Your LMP-based due date and ultrasound-based pregnancy age may not always match exactly. This can happen if ovulation occurred earlier or later than expected, your cycles are irregular, or the first day of the last period is uncertain.
An early pregnancy ultrasound can provide additional dating information by measuring the developing pregnancy. When there is a meaningful difference between the LMP estimate and an early scan, your obstetrician will decide which date should be used for ongoing pregnancy care.
Once a reliable estimated due date has been established, later scans are generally used more for monitoring fetal growth than for repeatedly changing the due date.
An EDD calculator by USG or ultrasound result should therefore be interpreted along with your menstrual history and clinical assessment rather than used independently to change your pregnancy dates.
When Is LMP Dating Most Useful?
LMP dating works best when you remember the first day of your last period and your cycles are reasonably regular.
When Can Ultrasound Dating Be Helpful?
Early ultrasound may be particularly useful when the LMP is uncertain, cycles are irregular, pregnancy dates do not match expected findings, or additional confirmation of gestational age is needed.
Pregnancy dating
Gestational Age Calculator: How Pregnancy Age Is Calculated from LMP
Gestational age describes how many completed weeks and days have passed since the first day of your last menstrual period. It is the standard way doctors describe how far a pregnancy has progressed.
A gestational age calculator counts from the LMP rather than from the date of conception. For example, when approximately two weeks have passed since conception in a typical cycle, the pregnancy may already be described as around four weeks gestation.
Gestational Age vs Fetal Age
Gestational age begins from the first day of the LMP. Fetal age is closer to the time since fertilisation and is therefore usually about two weeks less in a typical menstrual cycle. Healthcare professionals normally use gestational age for pregnancy care, scan timing and antenatal planning.
What Does POG Mean in Pregnancy?
POG means period of gestation. It is another way of expressing how far the pregnancy has progressed, usually in completed weeks and days. A POG calculator and a gestational age calculator therefore address very similar pregnancy-dating needs.
How Is Gestational Age Calculated from LMP?
Start with the first day of your last menstrual period and count the completed weeks and additional days to the current date. For example, 12 completed weeks plus three additional days is recorded as 12 weeks and 3 days of gestation.
Pregnancy stages
Pregnancy Weeks, Months and Trimesters
Pregnancy is divided into three trimesters, with each trimester representing a different stage of fetal development and maternal changes.
| Pregnancy Month | Approximate Weeks | Trimester |
|---|---|---|
| Month 1 | Weeks 1 to 4 | First |
| Month 2 | Weeks 5 to 8 | First |
| Month 3 | Weeks 9 to 13 | First |
| Month 4 | Weeks 14 to 17 | Second |
| Month 5 | Weeks 18 to 22 | Second |
| Month 6 | Weeks 23 to 27 | Second |
| Month 7 | Weeks 28 to 31 | Third |
| Month 8 | Weeks 32 to 35 | Third |
| Month 9 | Weeks 36 to 40 | Third |
Pregnancy is normally tracked in weeks and days because calendar months are not equal in length. A pregnancy month calculator by week or pregnancy week chart can help with everyday understanding, but your gestational week remains the more precise medical measure.
For a more detailed week-to-month explanation, see our Pregnancy Weeks to Months: Week and Month Chart.
The total weeks of pregnancy are usually around 40 when measured from the first day of the last menstrual period.
A pregnancy may normally progress beyond the estimated due date, and your maternity team will advise you about monitoring and next steps based on your individual pregnancy.
A pregnancy trimester calculator can help identify which stage you are currently in, but your healthcare appointments and scan schedule should follow your doctor's advice.
Due date accuracy
How Accurate Is a Pregnancy Due Date?
An accurate due date calculator can provide a useful estimate, especially when the date of the last menstrual period is known and cycles are regular.
However, the due date is not an exact prediction of the day labour will begin.
Factors that can affect pregnancy dating include:
- Irregular menstrual cycles
- Uncertainty about the last period date
- Ovulation occurring earlier or later than expected
- Differences between LMP dating and early ultrasound measurements
- IVF treatment timing
Your doctor may use an early ultrasound to confirm or refine gestational age when needed.
Pregnancy dating
Can My Due Date Change?
Yes. Your estimated due date may change if an early ultrasound shows that the pregnancy is at a different gestational age than originally estimated from the last menstrual period.
Doctors generally consider the timing of the ultrasound, the difference between the two estimates and your menstrual history before revising the due date.
Once pregnancy dating has been established with reliable information, the due date is not usually changed repeatedly based on later fetal size alone.
Known due date
What If I Already Know My Due Date?
If you already know your expected delivery date, you can work backwards to estimate your current pregnancy week.
A pregnancy week calculator by due date can help provide an approximate pregnancy timeline and show how many weeks may remain.
Your medical records and confirmed due date from your doctor should remain the primary reference for clinical decisions.
Pregnancy duration
What Is the Normal Duration of Pregnancy?
The human gestation period is commonly described as approximately 40 weeks when measured from the first day of the last menstrual period.
A normal pregnancy can vary in duration. Labour does not necessarily begin exactly on the estimated due date.
The due date serves as a reference point for pregnancy monitoring rather than a fixed prediction of the delivery day.
Frequently Asked Questions
Find answers to common questions about pregnancy calculations, due dates, and gestational age.
How do I use the pregnancy due date calculator?
Enter the first day of your last menstrual period and your average menstrual cycle length into the pregnancy calculator. The calculator will estimate your pregnancy week, gestational age and expected due date.
Use the result as an estimate and discuss pregnancy dating with your doctor when required.
How is my due date calculated?
A standard due date calculator generally adds about 280 days, or 40 weeks, to the first day of your last menstrual period.
Your doctor may also consider your menstrual cycle length, ultrasound findings or IVF treatment dates when confirming your expected delivery date.
How do you calculate pregnancy weeks from the due date?
If your confirmed due date is known, pregnancy weeks can be estimated by comparing the current date with the expected delivery date.
A full pregnancy is generally counted as approximately 40 weeks.
A pregnancy calculator can make this calculation easier.
How many weeks pregnant am I?
Pregnancy weeks are usually counted from the first day of your last menstrual period.
A pregnancy week calculator can estimate how many completed weeks and days have passed and identify your approximate pregnancy month and trimester.
How do I use a pregnancy calculator?
To use a pregnancy calculator, enter the first day of your last menstrual period and any other information requested by the calculator, such as average cycle length.
The calculator uses these details to estimate your pregnancy week and due date.
How do I calculate pregnancy weeks?
Count from the first day of your last menstrual period to the current date.
Healthcare professionals count pregnancy from the last menstrual period rather than the estimated date of conception.
A pregnancy week calculator can perform this calculation automatically.
How do I calculate how many weeks pregnant I am from my last period?
Identify the first day of your last menstrual period and count the number of weeks that have passed since that date.
A pregnancy calculator uses the same basic principle to estimate gestational age.
How does the pregnancy due date calculator work?
A pregnancy due date calculator uses your menstrual dates to estimate when a 40 week pregnancy may reach its expected delivery date.
The result is an estimate because ovulation and conception do not occur at exactly the same time in every menstrual cycle.
What is the estimated date of delivery?
The estimated date of delivery, also called EDD, is the approximate date when a pregnancy reaches 40 completed weeks based on established pregnancy dating.
An EDD calculator can provide an initial estimate using your last menstrual period.
How likely am I to give birth on my due date?
The estimated due date is not a guaranteed delivery date. Labour may begin before or after it.
Your maternity team monitors pregnancy progression and will guide you based on gestational age, maternal health and fetal wellbeing.
How soon can I take a pregnancy test?
A home pregnancy test detects the hormone hCG after implantation.
Testing is generally more reliable around the time your period is expected or after a missed period. Testing too early can sometimes produce a negative result even when pregnancy has occurred.
How do I calculate EDD from LMP?
To calculate EDD from LMP, start with the first day of your last menstrual period and estimate approximately 280 days forward.
An LMP EDD calculator performs this calculation automatically.
Your doctor may refine the estimate if your cycles are irregular or ultrasound dating differs significantly.
What is an LMP calculator?
An LMP calculator uses the first day of your last menstrual period to estimate pregnancy week, gestational age and expected delivery date.
It is most useful when the LMP date is known and menstrual cycles are reasonably regular.
How do I calculate gestational age from LMP?
Gestational age is counted from the first day of the last menstrual period.
To estimate it, count the weeks and days that have passed since that date.
A gestational age calculator can make this easier by converting your LMP date into your current pregnancy age.
What is the difference between gestational age and fetal age?
Gestational age starts from the first day of the last menstrual period.
Fetal age is closer to the time since conception and is usually about two weeks less than gestational age in a typical menstrual cycle.
Doctors normally use gestational age during pregnancy care.
How many weeks are there in a normal pregnancy?
A normal pregnancy is commonly estimated at around 40 weeks from the first day of the last menstrual period.
The actual pregnancy duration in weeks can vary, and delivery does not always happen exactly at 40 weeks.
How many months pregnant am I?
Pregnancy months are approximations because pregnancy is measured more accurately in weeks.
For example, weeks 1 to 4 are commonly described as the first month, while weeks 36 to 40 fall within approximately the ninth month.
A pregnancy month calculator can help with this conversion.
How do I convert pregnancy weeks to months?
There is no exact one to one conversion because calendar months vary in length.
A pregnancy weeks and months chart can provide an approximate conversion, but healthcare professionals usually use pregnancy weeks for greater accuracy.
Can an ultrasound change my due date?
Yes. An early ultrasound may lead your doctor to revise the due date if the ultrasound based gestational age differs significantly from the LMP estimate.
Early pregnancy ultrasound is generally more useful for dating than measurements taken much later in pregnancy.
Is pregnancy counted from conception or from the last period?
Pregnancy is normally counted from the first day of the last menstrual period, not the estimated conception date.
This is why gestational age is generally about two weeks greater than the actual time since conception in someone with a typical cycle.
Can I calculate pregnancy week if my periods are irregular?
You can use a pregnancy calculator, but LMP based results may be less precise when cycles are irregular.
An early ultrasound may provide a more useful estimate of gestational age. Discuss uncertain pregnancy dates with your gynecologist.
What happens if I do not remember my last period date?
If you cannot remember your LMP, your doctor may use an early ultrasound and other clinical information to estimate gestational age.
Do not guess your last menstrual period simply to generate a calculator result if the date is uncertain.
Can I calculate my due date after IVF?
Yes. An IVF due date calculator uses the embryo transfer date and embryo age rather than relying only on the last menstrual period.
Your fertility specialist can confirm your pregnancy dating and expected delivery date.
Is an IVF pregnancy week calculated differently?
The way pregnancy weeks are expressed remains the same, but IVF provides more precise information about fertilisation and embryo transfer timing.
A pregnancy week calculator IVF calculation therefore uses known treatment dates to estimate gestational age.
What is a pregnancy date calculator?
A pregnancy date calculator estimates important pregnancy dates such as gestational age, pregnancy week and expected due date from information such as LMP or a known due date.
It does not determine the exact date of conception in most naturally conceived pregnancies.
What is the difference between a pregnancy calculator and a due date calculator?
A pregnancy calculator may show your current pregnancy week, month, trimester and estimated due date.
A due date calculator focuses primarily on estimating the expected date of delivery.
Both may use your last menstrual period as the starting point.
Can a pregnancy calculator tell the exact conception date?
No. In a naturally conceived pregnancy, a calculator cannot reliably determine the exact conception date because ovulation timing can vary and sperm may survive for several days.
IVF pregnancies provide more precise treatment dates.
Can a pregnancy calculator predict the baby's gender?
No. A pregnancy calculator estimates dates and gestational age. It cannot predict or determine the baby's sex based on the due date, conception date or pregnancy week.
Can my cycle length affect my due date calculation?
Yes. Standard pregnancy dating often assumes a menstrual cycle of around 28 days.
If your cycles are consistently shorter or longer, ovulation may occur at a different time. Your doctor may use additional information to confirm pregnancy dating.
What information should I keep ready for my first pregnancy appointment?
It can help to note:
- The first day of your last menstrual period
- Your usual menstrual cycle length
- The date of your positive pregnancy test
- Current medications and supplements
- Previous pregnancy or medical history
- Any pain, bleeding or other symptoms
If you need assistance connecting with the appropriate Motherhood Hospitals team, you can write to writetous@motherhoodindia.com.
Is an IVF pregnancy week calculated differently?
The way pregnancy weeks are expressed remains the same, but IVF provides more precise information about fertilisation and embryo transfer timing. Therefore, an IVF pregnancy week calculator uses known treatment dates to estimate gestational age.
What is the difference between an LMP calculator and an EDD calculator?
An LMP calculator uses the first day of your last menstrual period to estimate pregnancy timing. An EDD calculator uses that information to estimate the expected date of delivery. In many pregnancy calculators, both calculations are performed together.
Is a gestational age calculator the same as a pregnancy week calculator?
They are closely related. Both estimate how far the pregnancy has progressed in weeks and days, usually from the first day of the LMP. Gestational age is the medical term commonly used by healthcare professionals.
What is a POG calculator?
POG stands for period of gestation. A POG calculator estimates the pregnancy's gestational age in weeks and days, typically using the LMP or another confirmed pregnancy-dating method.
Pregnancy dating guides
Learn More About Pregnancy Dating and Pregnancy Weeks
Pregnancy Weeks to Months
Understand how to easily convert your pregnancy weeks into months for tracking milestones.
Read More →How Pregnancy Due Date is Calculated
Discover the medical methods used to accurately calculate your expected delivery date.
Read More →When to Take a Pregnancy Test
Learn the ideal timing for taking a pregnancy test to ensure accurate and reliable results.
Read More →Best Time to Get Pregnant After Period
Find out the optimal window of opportunity during your cycle to increase your chances of conception.
Read More →From Your Last Period to Your Due Date
Pregnancy dating can feel confusing, especially in the early weeks. This explainer breaks down how your last menstrual period is used to estimate how far along you are and your expected due date, while also explaining why the final dating may change after an ultrasound.
Language access
Use the Pregnancy Calculator in Your Preferred Language
Access pregnancy calculator information and pregnancy dating guidance in your preferred language as Motherhood Hospitals expands its vernacular health resources.
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