Calculate your pregnancy due date and track your progress.
The date estimate is calculated from the entered cycle, last menstrual period, conception date or gestational reference using standard calendar intervals.The estimate applies standard calendar intervals to the selected last-period, conception, due-date or cycle information. Irregular cycles, assisted reproduction, ultrasound dating and clinical findings can change the relevant date.
Your due date Calculator - for use of information purposes: Most calculators will tell you when to expect to give birth. Some will ask to start by, (mostcommonly) the first day of the last menstruation. Other inputs thatmaybe askedforare; date of conception OR any pregnancy details, etc..
What you willget is anestimated duedate of conception andgestational periodor date of the delivery in addition to a possible gestionalageof pregnancy. Acalculated due date isnotalways goingto beexactas many things that might influence the dating ofa pregnancy: cycle lenght, ovultion date of conception, scan resultsetc.,might lead todate that can beoff as ofa few days
If you don’t know the start date of your last menstrual period, don’t just plug in a date that’s handy to get an outcome. Without knowledge of your last LMP, using this method for a date calculation may not be very accurate.
Most calculators of the estimated due date Based on LMP Calculate the estimated delivery date by adding approximately 280 days, or 40 weeks to the first day of your last normal menstruation cycle (this calculator is based on the traditional 28 day, with ovulation 14 days from the last day of period date calculation).
This is a best guess at a date and not a prophecy of labor. Many factors are in play and some pregnant women deliver before their due date and others after theirs.
if more is known about the date of conception about some of the figures around 266 days (from conception rather than LMP of 280 days).
For the standard last-menstrual-period method:
Estimated Due Date = First Day of LMP + 280 Days
Because 280 days equals 40 weeks:
Estimated Due Date = First Day of LMP + 40 Weeks
The associated computation is typical of Naegele's rule. In the traditional form, the due date could be:
LMP + 1 Year − 3 Months + 7 Days
For a cycle that differs substantially from 28 days, some calculators adjust the estimate using the difference between the individual's cycle length and 28 days:
Adjusted Due Date = LMP + 280 Days + (Cycle Length − 28 Days)
This adjustment is an estimate and should not be interpreted as a clinical dating rule for every pregnancy.
Suppose the first day of the last menstrual period was January 1, 2026, and the calculator uses the standard 28-day cycle assumption.
Starting date: January 1, 2026
Estimated pregnancy length: 280 days
Calculation: January 1, 2026 + 280 days
Estimated due date: October 8, 2026
This date is merely an estimation according to the LMP procedure. Thus, October 8 is only a calculated prediction and not a determined exact date. However, the final result of a childbirth can be different for several weeks.
Expected Due Date Estimated time of delivery when a pregnancy reaches the expected term of 40 weeks when counting dating from first day of last menstrual period.
You can think of the expected delivery date as an indicator, rather than a commitment. You will find a relatively small minority of babies are born on the estimated date.
Pregnancy dating can be revised when additional clinical information becomes available. A healthcare professional may consider menstrual history, physical examination, ultrasound measurements, and other relevant information when establishing or confirming gestational age.
Estimated Due Date An estimated due date is not a guarantee of when labor will occur. Each pregnancy can be of longer duration as expected when we assume a woman is pregnant for 40 weeks.
The difference is crucial for planning using the calculator. while date the average may aid in ordering prenatal and planning moreGenerally, not should never be treated by the baby.
The LMP system relies on an accurate knowledge of the date of the first day of a woman's last menstrual period. Some irregularities, such as spotting and irregular bleeding or not being sure of the last menstrual period date, can make using LMP estimates unreliable.
That standard 280 day countdown is based on the idea that your cycles are 28 days long. If your cycle is shorter or longer you might ovulate earlier or later than they account for and that changes the LMP estimation method.
Ovulation does not usually fall on the same day for everyone and each person's cycle varies as well so estimating this alone based on your LMP will result in an inexact measurement.
If the date of conception is known with some certainty, this may provide an alternative point of commencement for an estimated date of delivery. Conception is not always easy to assess.
Ultrasound measurements may also offer helpful information about the gestational age if the menstrual history is in doubt. The person managing the pregnancy can then decide which dating is most suitable.
Post-IVF Dating Using Procedure and Embryo Date Information rather than LMP If your pregnancy occurred through an IVF, fertilization, other assisted reproductive techniques: You will get a specific gestational dating based upon the assisted reproductive procedure. Make use of the particular estimated week of the due date given you from the fertility team or your prenatal health care staff.
Usually the date of gestation dates from your last menstrual date (which precedes your conception date by about two weeks if you ovulate typically).
For example when you read that a pregnancy is '8 weeks pregnant' most professionals have counted eight weeks since LMP (Last Menstrual Period) not from when the conception took place.
The Due Date Calculator estimates conception date as close as possible to your likely ovulation. However, it’s not 100% accurate for when you actually conceived or your baby would be born and shouldn’t be used as your official clinical pregnancy dating tool.
If you are pregnant and have a query about estimated date of delivery, gestation age, ultrasound dating or any aspect of your pregnancy speak to a suitably trained health care professional.
Using the average LMP calculation means that your due date is set by taking the first day of the LMP and adding 280 days or 40 weeks to calculate.
A conventional rule that uses the first day of the last menstrual period (LMP) as a way to calculate due date; the rule uses approximately 280 days.
For a reliable LMP calculation, the date of the first day of the last menstrual period is needed. When LMP is unknown or uncertain other information including clinical examination and ultrasound, are often used for pregnancy dating.
It can. The typical LMP calculation method relies on a 28-day cycle, meaning your estimate will be way off if your cycle is longer or shorter or your ovulation happens too soon or too late.
For standard calculations, it counts 40 weeks or 280 days from the first day of the LMP. This is a rough estimate of the number of weeks in pregnancy, and it does not signify that the woman will have her baby at week 40.
Yes, Ultrasound may give some indications of the age of the pregnancy and may support a clinician changing the initial appraisal if necessary especially when the LMP is unreliable.
Enter the best available date and the cycle information requested. Use the output for planning, then rely on clinical assessment for medical decisions and official pregnancy dating.
For the simplest basic technique you could just begin with the very day of the last menstruation phase and calculate in 280-day to reach your own approximate distribution date. This depends on some traditional 40 weeks expecting term format that will estimate for the day of delivery using date ranges.
| Starting Point | Estimated Pregnancy Length | Calculation |
|---|---|---|
| First day of LMP | 40 weeks | LMP + 280 days |
| Known conception date | Approximately 38 weeks | Conception date + 266 days |
The two modes calculate differently: gestational age is calculated from LMP, and in the normal cycle fertilization occurs later.
The average LMP method is designed to be used for a typical 28 day cycle. If you typically have a cycle longer or shorter than 28 days then the estimate in the adjusted LMP version may differ from the standard result.
A simplified adjustment can be represented as:
Adjusted Due Date = LMP + 280 Days + (Cycle Length − 28 Days)
For example, if a person's usual cycle is 32 days, the simplified adjustment is four additional days compared with the standard 28-day assumption.
Cycle adjustment: 32 − 28 = 4 days
Adjusted estimate: Standard due date + 4 days
This is simply a math correction only, should not substitute the standard way of determining gestational age with regards to late periods especially if your cycle month to month is not the same.
If you can make a pretty good guess at the date of conception, you can approximate a due date by adding roughly 266 days, or 38 weeks to that date.
Estimated Due Date = Conception Date + 266 Days
For example, if conception occurred on January 15:
January 15 + 266 days = October 8
Unfortunately It can’t be pinpointed exactly when the conception had occurred so an estimated time can influence the result in an unknown factor.
This usually is conveyed in weeks and days, rather than solely a specific date. Gestational age is calculated in this way from the beginning date of your LMP.
| Gestational Age | Approximate Position in a 40-Week Timeline |
|---|---|
| 4 weeks | Approximately 36 weeks before the estimated due date |
| 8 weeks | Approximately 32 weeks before the estimated due date |
| 12 weeks | Approximately 28 weeks before the estimated due date |
| 20 weeks | Approximately 20 weeks before the estimated due date |
| 28 weeks | Approximately 12 weeks before the estimated due date |
| 32 weeks | Approximately 8 weeks before the estimated due date |
| 36 weeks | Approximately 4 weeks before the estimated due date |
| 40 weeks | Estimated due date |
These are timeline calculations based on the estimate of 40 weeks, and are not predictions of an individual's pregnancy's timeline.
Do not use an LMP-based calculator if you cannot recall the first day of your last period. Do not select an arbitrary date just for the sake of a resulting due date.
Healthcare professionals have several other resources to rely on when estimating a woman’s gestational age. Depending on the circumstances, a fetal ultrasound could be a great determining factor for a pregnancy’s age.
The originally calculated initial due date can vary as more information helps calculate the estimated due date in an alternative way. This occurs in cases with irregular menstrual cycles, uncertain dating from history or due dating with other information conflicting with calculation.
It would be prudent not to let the result from an online calculator replace the adjusted clinical EDD. Clarify estimates with healthcare provider responsible for pregnancy care.
The estimated due date is an estimate based to give you dates during the pregnancy. The date it gives you is based on assumptions for how long a pregnancy is and every pregnancy is a different length of time.
Let the calculated date inform you about your approximate timeline of pregnancy but work with your prenatal care team to date the pregnancy clinically, monitor it and make other management decisions.
Uneven cycles can affect the accuracy of dating an LMP estimate, since the timing of ovulation may be different than what is typically predicted in the 28-day cycle framework.
When having regularly abnormal cycles the result of the calculator cannot be used other than a rough guide. Clinical data may be the most suitable to provide for accurate pregnancy dating.
You should talk with your pregnancy care provider about what due date is calculated if: LMP unclear; have irregular cycles or if the calculation and clinical estimate are off significantly. If you question how the pregnancy has been dated.
The calculator is intended as an informational estimation only and should not be used to help make decisions regarding pregnancy care, testing, treatment or delivery timing without proper medical advice and consideration.