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Calculating due date after miscarriage no period


Due Date Calculator — Amazingly Accurate Pregnancy Calculator

First day of your
last period:

Please choose the day your most recent period started.

Average cycle: 20 days21 days22 days23 days24 days25 days26 days27 days28 days29 days30 days31 days32 days33 days34 days35 days36 days37 days38 days39 days40 days41 days42 days43 days44 days45 days

or

Date you
conceived:

Conception is approximately two days after intercourse.

Already know your due date? Click here

Pregnancy Week by Week Universal Header

 

Pregnancy due date calculator video

Learn how to calculator your pregnancy due date in this video.

When is my baby’s due date?

So you got your positive pregnancy test, you’re feeling some early signs of pregnancy, and now you’re wondering, “when is my baby’s due date?” We’ve got you covered with the Mama Natural due date calculator!

Enter your information in the due date calculator above and discover the best estimate for when your little bundle of joy will make his or her appearance.

How does this due date calculator work?

Because you may not know exactly when you ovulated or conceived, a due date calculator will typically calculate your estimated due date based on your last menstrual period (LMP).

Our online due date calculator uses a simple method to calculate your due date.

  • Your due date is estimated to be 40 weeks after the first day of your LMP
  • Your cycle is assumed to be 28 days long, with ovulation occurring at day 14
  • Therefore the calculator adds 280 days (40 weeks) to your LMP

This method of due date calculation is known as Naegele’s rule (more info on this below).

Due date calculator quote Our standard due date calculator adds 280 days (40 weeks) to the date of your last menstrual period (LMP)

My cycle isn’t 28 days. Will this due date calculator work for me?

Yes. The logic behind our pregnancy calculator works as follows:

  • The average cycle length is 28 days
  • If your cycle length is shorter, your due date will be earlier
    • For every day your cycle is shorter, your due date moves one day earlier
  • Similarly, if your cycle is longer, your due date will be later
    • For every day your cycle is longer, your due date moves one day later

What is the date of conception due date calculator illustration

How do you calculate due date from conception?

If you know when you conceived, our pregnancy calculator calculates your due date by adding 38 weeks to the date of conception. This method of calculation may be more accurate than a LMP due date calculation if you have irregular or consistently longer or shorter cycles than 28 days.

What exactly

is the date of conception?

The date of conception is the day that the egg and sperm meet.

Women who track their ovulation may know their exact date of conception. But for many women, date of conception can be tricky to pinpoint.

Sperm can live in a woman’s body for up to five days, and the ovum (egg) can live for up to 24 hours after being released. In other words, you have a six-day window where you could potentially get pregnant each month.

Do you already know your due date but want to know when you likely conceived? Try our reverse due date calculator.

What is an estimated due date (EDD)?

An estimated due date (EDD) is a “best guess” as to when baby might be born based on a due date calculator like this one.

However, only 4% of babies are born on their due date! Whereas 80% of babies are born within the window of two weeks before and two weeks after your due date calculator results. (See “due month” section below.)

Baby due date on a calendar with pregnant woman background – only 4% of babies are born on their due date

What is “gestational age?” Can it be different than what the calculator shows?

Gestational age (GA) is the term used to describe how far along the pregnancy is and how long baby has been gestating (growing in the uterus).

If you get an ultrasound you may notice a “GA” on the image with a number of weeks and days. This figure is based on how the baby is measuring, not on your LMP, which the due date calculator uses.

It’s normal for these dates to not match up perfectly. If there are significant differences in the dates, your doctor may want to dig deeper to determine conception date. As a result, your midwife or doctor may change your due date based on the ultrasound gestational age.

Early ultrasounds are very accurate when dating a pregnancy and can be helpful if you don’t know your LMP or your periods are irregular.

Note that you don’t have to have an early ultrasound, especially if you are fairly certain of your cycle length and conception window. This study shows that early dating ultrasounds don’t change the incidence of induction.

How are the weeks of pregnancy calculated?

The 40 weeks of pregnancy begin on the first day of your last menstrual period.

This can be a little confusing because, for most people, conception doesn’t occur until day 14 of the menstrual cycle. So yes, you aren’t actually pregnant during those first two weeks of pregnancy.

Here’s a more in-depth answer to that perennial question of How many weeks pregnant am I?

What is a

“due month?”

A “due month” is a more accurate timeframe for when you can expect to deliver your baby. Only 4% of babies are born on their due date. Whereas 80% of babies arrive either two weeks before the due date or two weeks after. Hence the term “due month.”

The length of a natural pregnancy can vary by as much as five weeks. (source)

A due month helps some mamas reduce the stress and fear of going past their due date.

To calculate your due month, simply subtract two weeks from your EDD given by your practitioner or our due date calculator and also add two weeks to your EDD. Voilà, your due month!

Yet another way to handle this tricky business of calculating your pregnancy calendar is to add two weeks to the end of your EDD and say, “Baby will be here before [that date].”

What is Naegele’s rule for due date calculation?

Naegele’s rule is what this due date calculator and pregnancy calendar is based on. Named after a German Obstetrician who practiced in the early 1800’s, Naegele’s rule predicts childbirth to occur 280 days after the first day of the last menstrual period.

However, Naegele’s rule assumes that your cycle is 28 days long with ovulation occurring on day 14, which isn’t the case for many women. So other ways of calculating your due date may be more accurate.

(How accurate is your due date? Find out in this post.)

Modern data suggests that women have their babies a few days after their due date on average. Studies like this one found that Naegele’s rule consistently places the due date about 2-4 days too early. So a better estimate may be 40 weeks and 3 days from LMP.

Alternatively, you can use our Advanced Due Date Calculator, which uses the Mittendorf-Williams rule to calculate your due date, which has been shown to be more accurate.

Due date calculator quote 2 Modern data suggests that Naegele’s rule places the due date about 2-4 days too early

What’s the Mittendorf-Williams rule?

This study done in 1990 showed that pregnancy lasted an average of 288 days past LMP for Caucasian first-time moms. For Caucasian women who were not first-time moms, their date of delivery averaged 283 days past LMP (3 days after Naegele’s rule predicted). This finding is known as the Mittendorf-Williams rule.

While Naegele’s rule is still the most widely used formula for a due date calculator, the Mittendorf-Williams rule is proving to be more accurate. But it’s a much more complex calculation, taking into account:

  • Maternal age
  • Race
  • Height
  • Weight
  • Number of pregnancies
  • Average luteal phase length
  • Maternal education
  • Alcohol during pregnancy
  • Coffee during pregnancy

Our Advanced Due Date Calculator uses the Mittendorf-Williams rule.

Related Resources

  • Our FREE Natural Pregnancy Week-By-Week Series ?
  • My Bestselling Natural Pregnancy Guide ?
  • Reverse Due Date Calculator ◀️
  • Natural Birth Stories ??
  • Baby Name Finder ?

Ready to calculate your due date?

First day of your
last period:

Please choose the day your most recent period started.

Average cycle: 20 days21 days22 days23 days24 days25 days26 days27 days28 days29 days30 days31 days32 days33 days34 days35 days36 days37 days38 days39 days40 days41 days42 days43 days44 days45 days

or

Date you
conceived:

Conception is approximately two days after intercourse.

Already know your due date? Click here

Working out your due date

Working out your due date | Pregnancy Birth and Baby beginning of content

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Key facts

  • You can calculate your estimated due date based on the date of the first day of your last menstrual period or with ultrasound (LMP).
  • Your due date is an estimation of when your baby may be born.
  • The average length of a pregnancy is generally about 40 weeks. Although babies are usually born between 37 and 42 weeks of pregnancy.
  • It is important to have an accurate due date so that you and your healthcare team can monitor your pregnancy and baby’s growth and to help keep you and your baby safe.
  • When you have your first appointment with your doctor or midwife, they will help you work out your due date.

How can I work out my due date?

After finding out you're pregnant, you will want to know how pregnant you are and when your baby is likely to be born. This can be done by working out your estimated due date.

You can calculate your baby’s estimated due date based on the date of the first day of your last menstrual period (LMP). Your baby will be ‘due’ around 40 weeks after the first day of your LMP. This method is particularly accurate if you have a regular menstrual cycle. For example, if you have a regular 28-day cycle, add 7 days to the date of the first day of your last period, then add 9 months.

If your cycle is longer or shorter than 28 days or irregular, working out your due date using the first day of your LMP can be more difficult and may also be more unreliable.

Another way your due date can be calculated is by using ultrasound. By measuring your baby’s size, doctors can work out how far along your pregnancy is. In early pregnancy (usually before 13 weeks) your doctor will measure the length from your baby’s head to your baby’s bottom. This is called the crown-rump length or CRL. Later in pregnancy, your doctor can measure different parts of your baby’s body, including your baby’s head, thigh bone and abdomen to work out an average size and an estimated due date.

Ultrasounds, particularly those done in your first trimester, are generally very accurate at dating your pregnancy, but sometimes there can be a difference in the due date when comparing LMP and ultrasound dates. If this happens to you, your doctor or midwife will explain which is most accurate according to your individual circumstance.

It's important to understand that your due date is only an estimate. The exact timing of your baby’s birth is unpredictable. Babies are considered ‘term’ and are usually born anywhere between 37 and 42 weeks of pregnancy. Only about 4 out of every 100 babies are born on their actual due date.

How does my menstrual cycle affect my due date?

The average menstrual cycle is around 28 days. However, the length of a menstrual cycle differs between people. Your menstrual cycle may be as short as 21 days or be as long as 35 days. If your menstrual cycle is longer, this means you ovulated later in your cycle and that your estimated due date will be later. If your menstrual period is shorter, this means that you ovulated earlier in your cycle and that your estimated due date will be earlier.

If you have an irregular cycle, meaning sometimes your menstrual cycle could be 28 days and other times 35 days, for example, it can be more difficult to accurately estimate your due date base on your LMP.

Why is it important to have an accurate due date?

It is important to have an accurate due date so that you and your chosen healthcare team can monitor your pregnancy appropriately and keep you and your baby safe. When you give birth to your baby it is important to know how far along you are in your pregnancy. Your doctors need to know whether your baby is being born early, on time or late.

If you go into labour early, it is important for your medical team to be prepared for various complications that can occur with prematurity. Your healthcare team may need to prepare to transfer your baby to a special care unit or NICU. If, on the other hand, you are overdue, your doctor or midwife may recommend you induce your labour (begin your labour) to prevent complications that can occur with being overdue. This will be done in consultation with you, taking into consideration your birthing preferences.

Can my due date change?

If you have a regular menstrual cycle and have used this to work out your due date, or if you have had an early dating ultrasound your estimated due date is unlikely to change later in pregnancy. Ultrasounds done later in pregnancy are not as accurate at dating your pregnancy due to variations in babies’ growth and development. For this reason, your due date calculated earlier in pregnancy will be most accurate and is unlikely to change.

If you haven’t had an early dating ultrasound, a second or third trimester ultrasound can be used to date your pregnancy.

If your due date has been changed, speak to your doctor or midwife to understand why.

When should I see my doctor?

Usually, you can work out your due date without seeing a doctor. Choosing to have an early dating scan, although recommended, is your choice.

However, there are a few situations when having an ultrasound scan early in pregnancy may be strongly recommended. You should see a doctor if you:

  • have a very long or irregular menstrual cycle or don’t know your LMP
  • became pregnant while taking the oral contraceptive pill
  • have any bleeding during your pregnancy
  • have a medical condition or illness that could affect your pregnancy
  • have had a previous miscarriage or ectopic pregnancy

Resources and support

Use the Pregnancy, Birth and Baby calculator to estimate your due date.

Speak to a maternal child health nurse

Call Pregnancy, Birth and Baby to speak to a maternal child health nurse on 1800 882 436 or video call. Available 7am to midnight (AET), 7 days a week.

Sources:
Royal Women's Hospital Melbourne (About periods), Queensland Government (Queensland Clinical Guidelines; Preterm labour and birth), Queensland Government (When complications occur), Australian Government Department of Health and Aged Car (Gestational age), New South Wales Government, (Fact sheet- Ultrasound in early pregnancy (before 12 weeks) – Dating scan)

Learn more here about the development and quality assurance of healthdirect content.

Last reviewed: September 2022


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Related pages

  • Antenatal care during your pregnancy
  • Early signs of pregnancy
  • Ovulation signs
  • Due date calculator

Need more information?

Baby due date - Better Health Channel

Pregnancy is calculated from the first day of your last period, not from the date of conception.