Due Date Calculator - Calculate Your Pregnancy
Result:
The due date calculator (also called a pregnancy calculator) helps answer the question: "When is my baby due?" Our tool estimates the due date for your baby's birth. In this article, you'll learn about pregnancy due dates and how to calculate them using different methods (Naegele's rule and conception date). You'll also discover explanations of terms like "LMP," "due month," and "conception date."
What is a Pregnancy Due Date?
Pregnancy typically lasts around 280 days or nine months, counting from the first day of your last menstrual period. Early pregnancy symptoms may appear in the first few weeks and can be confirmed with pregnancy tests that detect hormones like human chorionic gonadotropin (hCG) in urine or blood.
Estimated Due Date (EDD)
An estimated due date (EDD) predicts the most likely day when labor may begin. However, many factors influence pregnancy length, so the date is only an estimation. Only about 4% of babies are born precisely on the calculated due date. Therefore, it's impossible to define the exact delivery day with 100% certainty.
What is a "Due Month"?
Since few babies are born on the exact due date, it's unrealistic to expect your calculated due date to be accurate. The "due month" refers to a time frame when your baby can be expected with proper gestation. About 80% of babies are born within two weeks before or after the expected due date.
To determine your due month, subtract or add two weeks to the estimated due date:
due month = due date ± 2 weeks
For example, if your estimated due date is May 3, 2019, your due month is May 17, 2019.
Here's an example of the calculation:
May 3, 2019 + 2 weeks = May 17, 2019
As you can see, the due month is the same as the calculated due date.
How to Calculate the Due Date
There are several methods to estimate the pregnancy due date, some simple and others more complicated. Keep in mind that all methods provide predictions, and your due date can change as your pregnancy progresses.
The due date can be defined using the following methods:
- Naegele's rule (based on the first day of your last period)
- The exact date of conception
- Mittendorf-Williams rule
- Doppler ultrasonography
- Pregnancy milestones
- Fundal height
The due date calculator provided by ThatCalculator.com uses the first two methods (first day of your last period based on Naegele's rule and date of conception).
What is LMP?
LMP stands for "last menstrual period." By convention, pregnancies are dated in weeks, starting from the first day of a woman's last menstrual period before becoming pregnant. The LMP refers to the first day of bleeding of your last period before pregnancy. Our calculator uses this data to calculate the due date. Following this counting method, a woman is considered six weeks pregnant only two weeks after her first missed period.
Naegele's Rule
Naegele's rule, also known as the "first day of LMP method," adds 280 days (40 weeks) to the first day of your last menstrual period:
due date = first day of LMP + 280 days
This method assumes regular 28-day cycles and that ovulation and conception occur precisely on the 14th
day of the cycle. Its accuracy depends on the mother's recall of the LMP first day and cycle length.
Some women experience light bleeding at the beginning of pregnancy, around the time they would normally
have their period, which means they may have been pregnant a few weeks earlier than they realize.
Periods aren't always precisely four weeks apart, so when the cycle is longer, the baby may be conceived
later than assumed, and when it's shorter, conception can happen earlier than estimated.
What is the Conception Date?
The conception date is when fertilization occurs, and a sperm meets an egg (fusion of gametes). From that moment, a zygote grows and divides rapidly, forming a new organism. Women who track their ovulation carefully may know their exact conception day, but it can be tricky for others to specify when they conceived. If a woman's menstrual periods are regular and ovulation occurs on day 14 of her cycle, conception takes place about two weeks after her LMP. After unprotected intercourse, sperm can live inside the vagina for up to seven days, and an egg can live up to 24 hours after its release. That gives an 8-day timespan of possibility to become pregnant in every cycle.
Conception Date Method
If you know the exact conception date, use the second calculation method in the due date calculator. Our due date predictor will add 266 days (38 weeks) to the entered date:
due date = date of conception + 266 days
How to Use the Our Pregnancy Calculator
Follow these steps to use the our pregnancy calculator and find out when your due date is:
- Choose between the methods: "first day of LMP" or "conception date."
- Enter the relevant dates based on the chosen method.
- Set your average cycle duration (in days) - optional, applies only to the "LMP" method.
- Read the calculated birth due date and the current week of your pregnancy.
- See the timespan for your due month.
Example Calculation
Let's use an example for our friend Emily to understand how the due date calculator works.
I. First Day of LMP Method:
Assume the first day of Emily's last period was March 1, 2023, and her average cycle duration is 28 days:
March 1, 2023 + 280 days = November 26, 2023
The due month is defined as:
Beginning of due month = November 26, 2023 - 14 days = November 12, 2023
End of due month = November 26, 2023 + 14 days = December 10, 2023
II. Conception Date Method:
Suppose Emily knows the exact conception date was March 15, 2023:
March 15, 2023 + 266 days = November 26, 2023
The due month is defined as:
Beginning of due month = November 26, 2023 - 14 days = November 12, 2023
End of due month = November 26, 2023 + 14 days = December 10, 2023
Time goes by quickly - soon, she'll choose a daycare, prepare for parenthood, and watch her baby grow up.
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FAQ
How many weeks is a full-term pregnancy?
A full-term pregnancy typically lasts between 37 and 42 weeks, with 40 weeks being considered the average duration. Babies born between 37 and 42 weeks are considered full-term.
Is it possible to get pregnant while already pregnant?
While it's extremely rare, it is possible to become pregnant while already pregnant. This is known as a "double pregnancy" or "superfetation." It occurs when a new egg is fertilized and implants in the uterus days or weeks after an initial pregnancy has already started.
What are the common signs of early pregnancy?
Some common early signs of pregnancy include:
- Missed menstrual period
- Tender, swollen breasts
- Fatigue or tiredness
- Nausea or morning sickness
- Food cravings or aversions
- Frequent urination
- Mood swings
Can I continue exercising during pregnancy?
In most cases, it's safe and beneficial to continue exercising during pregnancy. However, it's essential to consult with your healthcare provider and make necessary adjustments to your exercise routine as your pregnancy progresses. Generally, low-impact activities like walking, swimming, and prenatal yoga are recommended.
When can I expect to feel the baby move?
First-time mothers may feel the baby's first movements, known as "quickening," between 16 and 25 weeks of pregnancy. For subsequent pregnancies, women may feel the baby move as early as 13 or 14 weeks.
What are the different pregnancy trimesters?
Pregnancy is divided into three trimesters:
- First trimester: Weeks 1-12
- Second trimester: Weeks 13-27
- Third trimester: Weeks 28-40
