How many weeks pregnant am I?

Use the handy due date calculator to find out when your bundle of joy is predicted to arrive.

In this article you'll learn about how your pregnancy due date is calculated. Learn about the different methods to calculate how many weeks pregnant you are.

Remember your due date is an estimate based on the average pregnancy length. In fact only 5% of women actually deliver on their expected due date. Most babies don't stick to that specific schedule and might come a bit earlier or later than planned.

What is an estimated due date during pregnancy?

The expected due date is the day your baby is likely to be delivered, based on the average length of pregnancy.

No-one can tell you the exact day your baby will be born, unless you have a planned Cesarean section! But the expected due date is important when you need may need blood tests and scans during prenatal care, as well as monitor your pregnancy milestones.

What is the chances my baby will arrive on my due date?

Remember your due date is an estimate based on the average pregnancy length. In fact only 5% of women actually deliver on their expected due date. Most babies don't stick to that specific schedule and might come a bit earlier or later than planned.

When did I conceive and how many weeks pregnancy am I?

If you know the date you conceived you can use the due date calculator above to work out the expected due date of your pregnancy.

The calculation is done by adding 266 days onto the date you conceived. Or simply use the due date calculator above to do the maths for you!

The date you had sex may not be the exact date of your pregnancy starts. This is because it can take several days for the egg from one of your ovaries to travel down the fallopian tubes and meet a sperm to start conception.

My period is late, how do I calculate my expected due date?

There are lots of medical reasons for a late period. You may have an irregular menstrual cycle, or you may have a problem affecting your hormone levels (endocrine condition, weight loss etc). These can all affect your period so it's a good idea to do a pregnancy test to make sure being pregnant is the cause!

If you have a menstrual cycle with a regular period at the same time each month, you can calculated your due date by from the first day of your last period.

Take the first date that last period started, add 280 days. You'll also need to add a correction to account for the average length of your menstrual cycle. The typical cycle length is 28 days, but this can vary for lots of women. The due date calculator will do this automatically.

Another way to do the calculation is to subtract three months from the first day of your last period and add seven days.

Not all women gave a regular cycle and you may not know your last period date. If you have irregular periods or you aren't sure of when you had your last period another method will be more accurate.

Can the midwife tell me my due date?

A healthcare provider, like your midwife or obstetrician, can also give you a more accurate due date as your pregnancy progresses.

During your physical exam the midwife will take regular measurements of your belly, from the top of the bump down to your pelvic bone.

This measurement can indicate due dates but is also affected by other factors like the size of your baby, the amount of fluid around the them, and the size and shape of a woman's body.

Will my due date change when I have a scan?

The most accurate expected due date is calculated during your ultrasound scan that should be done at your 12 weeks prenatal visit.

During the scan the midwife or sonographer will take measurements of the baby, including their length and the fluid around their spine. This gives the most accurate measure of the pregnancy due date. Your due date will be changed to reflect these measurements.

The date based on these these measurements give a more accurate due date and this should not change again after this.

Why is it important to know my expected due date?

Even though your due date usually can't tell you the exact date your baby will arrive, it is still a really important piece of information. It's used to determine the date you may need a blood tests or scans, and used to determine pregnancy milestones.

How long does the average pregnancy lasts?

Most pregnancies last anywhere from 36 to 42 weeks.

The average used to pregnancy week is based on a 40 week pregnancy that is calculated from the first day of the last menstrual period to the expected due date.

It's whole pregnancy is divided into into three trimesters, each lasting around three months. It's totally normal for pregnancies to vary in length by quite a few weeks!

However beyond 42 weeks your healthcare provider may suggest planning for an induction of labour. This is because the baby can become too large which can cause distress and difficulties during labour.

Calculating due date by last period

not conceived until ovulation and the fertilisation of the egg, which usually happens at least 10 days after the first day of the mother's last menstrual period. Because there are many factors surrounding conception, it is difficult to pinpoint an exact date of conception. This calculator helps to estimate the date range of real conception and a possible range of days during which sexual intercourse might have led to conception. There are a few methods that can be used to estimate the conception dates. Last Menstrual Period Conception usually occurs

Can I plan my due date?

You can roughly plan your due date if you're trying to get pregnant but tracking your ovulation and conception. However, it's not possible to exactly plan when a baby will arrive because even a typical pregnancy can last between 36 and 40 weeks.

Could my baby's due date change?

Yes, your due date can change when you have your ultrasound scan at around 12 weeks pregnant. The measurements taken at the scan are used to make the most accurate estimate of your due date.

Is a conception calculator the same as a due date calculator?

A conception date calculator and due date calculator measure the same things. However a conception date calculator works in reverse and will tell you the date you are likely to have conceived if your know how many weeks pregnancy you are.