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How Many Weeks Pregnant Am I? – Pregnancy Calculator

How Many Weeks Pregnant Am I? - Pregnancy Calculator

Congratulations on your pregnancy! Are you wondering ‘How many weeks pregnant am I’? Well, good news! Our pregnancy calculator uses standard method used by doctors, to work out how many weeks pregnant you are based on the first day of your last menstrual period, and allows you to adjust the number of days in your menstrual cycle. The pregnancy calculator will also estimate the due date of your baby, and the conception date.

Note: The calculations provided are only estimates based on averages and should be treated as such. You should consult an obstetrician if you require a proper diagnosis.

Pregnancy Due Date Calculator – Input Your Details
How Many Weeks Pregnant & When Is Your Baby Due?
It is important to note that the calculations made by the above pregnancy calculator are only estimates based on averages. In fact, less than 10% babies are born on their estimated due date.

Want to know more on what’s happening at ? Read about in our Pregnancy Week By Week guide. From the emotional and physical differences you can expect, to advice on diet, health and wellbeing – you’ll find a wealth of information to help you through the different stages of your pregnancy journey.

How Many Weeks Pregnant Am I?

To work out how many weeks pregnant you are, and your due date, you will need to know the first day of your last menstrual period (LMP) – when your last period began. Simply enter this information into our calculator and click the ‘Calculate’ button. The pregnancy calculator will also estimate the conception date.

How Do I Calculate How Many Weeks Pregnant I Am?

Your due date isn’t calculated from the day you conceive – even if you know when you ovulate. There is no way to know that the sperm fertilised the egg on that same day – an egg can be fertilised for 24 hours after ovulation, and sperm can survive for three days after intercourse.

Your due date is calculated based on the date your last period started, and assumes you have a regular cycle. The first day of your last period is considered the first day of your pregnancy. 40 weeks is then added to this to give you your estimated due date, and an indication of how many weeks pregnant you are.

Why Is My Due Date Calculated By The First Day Of My Last Period?

It is standard practice for doctors to estimate due dates from the first day of your last menstrual period. To calculate your due date you need to know the date of your last period, the length of your cycle and that your cycle is regular.

If you don’t know the length of your cycle you can leave it as the default of 28 days, which is considered a standard cycle.

You may be interested to know that the menstrual and ovulation period count as the first two weeks of pregnancy, even though you aren’t actually pregnant!

**Due dates can be revised based on the size of your baby during the viability scan (also known as a dating scan)**

How Accurate Is The Pregnancy Calculator?

Our calculator uses the same method that doctors and obstetricians use for estimating how many weeks pregnant you are and your due date.

Any estimation of due date is always just that – an estimate – data from the Perinatal Institute says that just 4% of babies are delivered on their due date.

What Trimester Am I In?

Once you’ve discovered how many weeks pregnant you are, you’ll likely be asking ‘Which trimester am I in?’ Your can find out which trimester you are in by comparing how many weeks pregnant you are to our guide, below:

First trimester: 1-12 weeks
Second trimester: 13-26 weeks
Third trimester: 27-40 weeks (or when you give birth to your little one)

What Can I Expect During My Pregnancy?

Read our pregnancy week-by-week guide for more information on what to expect throughout your pregnancy, including the physical and emotional changes you’re likely to experience.