Pregnancy due date calculator: find out when your baby is due

Last modified on Wednesday 7 April 2021

This page contains affiliate links, which means we may earn a small amount of money if a reader clicks through and makes a purchase. All our articles and reviews are written independently by the Netmums editorial team.

If you've just found out you're pregnant, congratulations! No doubt you'll be dying to know when the baby's due so you can get planning. What better place to start than with our very own pregnancy due date calculator.

Whether you've been trying to conceive for a while or got pregnant quickly, there's nothing better than seeing that BFP on your pregnancy test. And it doesn't take long to start wondering when exactly you'll be having this baby.

Your GP will be able to give you a rough estimation but why wait until then?

Our handy pregnancy due date calculator can tell you in seconds.


Simply put in the date of your last period and the rough length of your cycle and click 'calculate' ...

Due date calculator

Select the first day of your last menstrual period and the average length of your menstrual cycle

How to calculate your due date

Our calculator works out your due date by:

  • taking the first day of your last period
  • adding on 40 weeks.

This formula works best if your cycle is every 28 days and your periods are regular.

Your GP or midwife will use a similar formula to work out your dates at your first booking appointment but you'll get a more precise due date once you have your dating scan. This takes place when you're around 12 weeks pregnant.

This is because the sonographer who does the scan can get a clearer picture of your baby's size and development. This enables you to get a more accurate due date.

How many weeks pregnant are you?

Our due date calculator above will also show you exactly how many weeks pregnant you are. Weeks of pregnancy are calculated from the first date of your last period, not from the day you conceived.

So if your last period ended 4 weeks ago, and you had sex to conceive a baby 2 weeks ago, you're considered to be 4 weeks pregnant.

There's also a difference between 'weeks of pregnancy' and 'weeks pregnant'. If you think about it, in your first week of pregnancy, you've not yet been pregnant for a full week, so you're 0 weeks pregnant. In your second week of pregnancy, you're 1 week pregnant, and so on.

How long are you pregnant for?

Although we talk about nine month pregnancies, in actual fact most women carry their baby for longer.

A pregnancy is usually at least 40 weeks – that's a good 9.5 months, almost 10 months if you go overdue!

However, everyone's pregnancy is different.

What's important is that your baby is considered full-term (ready to be born) from 37 weeks. Anything earlier and it'll be considered preterm or premature and may need assistance with breathing and feeding from an intensive care unit.

If you reach your due date and keep going with nothing happening, you may need to be induced to help get the baby out.

Being pregnant for longer than 42 weeks isn't usually recommended as it can increase your risk of complications.

According to the NHS:

'There's a higher risk of stillbirth if you go over 42 weeks pregnant, although most babies remain healthy.

'At the moment, there's no way to reliably predict which babies are at increased risk of stillbirth, so induction is offered to all women who don't go into labour by 42 weeks.'

How accurate is your due date?

Very few babies are born on their estimated due date and our pregnancy calculator is just to give you a guide!

According to NCT, 'only about 5% of babies are born on their due date'.

It reports that 'around 80% of babies are born between 38 and 42 weeks of pregnancy'.

'Try to remember that your due date is only a "likely" time for birth,' it adds.

Join a Netmums due date club

Now you know you're due date why not join in the chat in our forum? You can find other mums with the same due dates and support or follow each other's pregnancy journeys. Who knows, you may even find a lifelong friend!

Join your due date club here.

And you can find out. what to expect week by week by signing up to our pregnancy emails below ...


Sign up for your weekly Netmums pregnancy emails

I have read and understood Netmums' Privacy Notice and Terms & Conditions

Join in the chat about due dates in our thread below!

Related stories

A week-by-week guide to your pregnancy

CHAT: conception and due date confusion

The best pregnancy apps to download

Netmums Newsletters

Yes, please! I want the best parenting news around

*By signing up you accept Netmums' Privacy Policy and Terms & Conditions.