Pregnancy & Due Date Calculator

icon of fetus

Use this pregnancy calculator to estimate your due date, your remaining length of pregnancy, your probability of giving birth on certain dates and how big your baby currently is. In addition, you can see a timeline of your baby's development. Choose to predict based upon your last period, the date given at your last ultrasound or your known due date.

  Click here to choose your last period date

  Click here to choose your last ultrasound date

  Click here to choose your projected due date

Processing calculations...


The results given by this pregnancy calculator should be used only as a guide and should not replace medical advice.

Whilst every effort has been made in building this tool, we are not to be held liable for any special, incidental indirect or consequential damages or monetary losses of any kind arising out of or in connection with it. This pregnancy calculator is here purely as an additional service to you. Do not use calculations for anything where loss of life, money, property, etc could result from inaccurate calculations.

Always speak to a Doctor or health professional for advice and guidance relating to your pregnancy.

How many weeks pregnant am I?

To calculate how many weeks pregnant you are, this calculator looks at the first day of your last menstrual period (LMP) and compares it to today's date. The first day of your LMP counts as the first day of your pregnancy. This calculation is based upon an average cycle of 28 days. If your cycle is different to 28 days, your calculation will vary based upon this.

You will find that the sonographer at your first ultrasound scan (often called the dating scan) will give you a more accurate idea of how many weeks pregnant you are by measuring your baby from its head to its bottom to form a determination.

How is my due date calculated?

This pregnancy calculator uses one of two methods to work out your due date. If you fill in the start date of your last period, it takes that date and adds 40 weeks (280 days) to that date (assuming you've chosen a 28 day average cycle). If you've chosen a different cycle, it will add or subtract days based upon that. If you choose to calculate by ultrasound date, the calculator will work out your due date based upon how far along you are on that date. This will likely yield a more accurate result.

Due date marked on calendar, with pregnancy test

How accurate is this pregnancy calculator?

It is important to remember that this pregnancy calculator is meant to be a bit of fun and the results contain guesswork (as with all 'predictions' about the future). Assuming it will be born naturally, there's obviously no way of knowing for certain when your baby will arrive. It is worth noting that only 5-7% of babies arrive on their due date. The vast majority are born two weeks either side. This calculator, as with all due date calculators, should be used only as a guide, to give you a little help with planning for your baby's arrival.

How do your due date graphs work?

The graphs display possible due dates based upon baby arrival data from a survey carried out by This survey relied upon correct information being input by each of the 9,000+ Mums who took part; it was not a scientific study.