Calculate your baby's due date
Using the first day of your last period, and your average menstrual cycle (this is the number of days from the start of one period to the day before the next one), it's possible to estimate the date you conceived. Pregnancy is counted as being 40 weeks long, so your due date is calculated at 280 days from conception. Don't worry – our tool will do those sums for you, just fill in your info below and the results will show on our calendar.
Due Date Calculator
So you're having a baby (hurrah!) but when exactly? Simply enter your details in our pregnancy due date calculator and we'll do the rest.
Enter the date your last period started
How long is your menstrual cycle?
How accurate are due dates?
At your 12-week scan (which can happen any time between 10 and 14 weeks), an ultrasound will be used to measure your baby and determine the stage of pregnancy you're at. The big date will then be confirmed with greater accuracy.
Remember, this date is not cast iron, but more an estimated due date at this stage. In fact, fewer than 5% of babies are born on the predicted day itself, but at least it gives you a rough deadline for buying the pushchair / painting the nursery / choosing a name.
How many weeks pregnant are you?
Based on the date your baby is due and/or the first day of your last period, you can count the number of weeks to see how pregnant you are. Once you know the magic number, find out what you can expect in the weeks ahead, using our pregnancy calendar.
Keep track of how your baby is developing week by week, the changes happening to your body and what appointments you'll have, as well as looking ahead to giving birth and life with a newborn (we know that part seems a long way off right now). In the meantime, chat with other mums-to-be who are at the same stage as you, by joining a birth club.