Pregnancy Due Date Calculator

Chinese version: 预产期计算器

The average length of human gestation is approximately 266 days from conception date (usually refers to as 9 months).
The average woman has cycles that lasted 28 days and she ovulated on Day 14 of her cycle.

The first day of your last menstrual period was January 1, 2010.
Assuming that your period is 28 days then conception date will be at : January15, 2010.
Counting 266 days from that point will show that your due date will be at: October 8, 2010.
Few factors can affect the due date:
Cycle duration: Although the average cycle is 28 days, it is perfectly normal to have a cycle that is as short as 21 days or even long as 33-35 days. For a teen, It is absolutely normal for cycle to last up to 45 days.
Ethnicity- i.e: Caucasian mothers with no children should add fifteen days to their pregnancy due date; Caucasian mothers who have children should add ten.
African-American and Asian mothers generally have shorter gestations; they should add eight days to the calculated due date.
Are you a first time mom? if not – how many pregnancies have you had before?
How accurate is your due date?
Two-thirds of all babies are born within ten days of their predicted due date
About 80% of the babies are born between week 38 and week 42
Only 5% of babies are actually born on their exact predicted due date

You are lucky to be a woman! Your pregnancy period lasts up to 9 months.

Elephants have the longest pregnancy duration among mammals: 20 to 22 months. The baby elephant is going to weight around 115Kg (a bit more than the baby carry). One of the shortest pregnancy periods in nature belongs to the Hamster: it is only 16 days.
But… when you are at the last days of your pregnancy, feeling heavy and just wait to deliver, just think about the poor Alpine Salamander of Southern Europe which holds the world's record of the longest pregnancy period on earth: 38 months (more than 3 years!)

Alpine Salamander – 3 years pregnancy African Elephant – 2 years pregnancy

These animals are added to the due data calculator below, so you can comfort yourself looking at their due data. Your newborn will already speak basic English when the Salamander baby will be just born.

How to use the pregnancy due data calculator:
This pregnancy calendar is based on the basic rules that was published more than 160 years ago (by Dr Naegele), enter:
The first day of your last menstrual period
Your average period cycle (in days). The default taken here is 28 days

The table will show you the estimated due date together with first and second trimester (usually refers to as week 12 and week 27).
Make sure to read the Disclaimer below before using this calculator.

Due Date Calculator

Enter the first day of your last menstrual period:

Your Average Menstrual Cycle
Likely conception date:
End of first trimester (12 weeks):
End of second trimester (27 weeks):
Your due date (40 weeks):
Get some proportions ...
Alpine Salamander's due date:
Elephant's due date:
The due date calculator is subject to mistakes and is provided for study purposes only.
The information provided is estimation only and should not be relied upon.
Only your Doctor can accurately calculate your estimated due date.
Information provided here is not intended to be a substitute for professional medical care or advice.
Use of the due date calculator indicates your acceptance of these terms.

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