Wondering when your baby might arrive?
Our pregnancy calculator helps you estimate your due date, track how far along you are, and work out your trimester. Whether you just found out you’re expecting or you are part way through and want to check how many weeks you are, this easy-to-use tool gives you a clear picture of your pregnancy timeline.
Remember: Every pregnancy is unique. This calculator provides an estimate based on average cycles, so your healthcare provider’s estimate may differ slightly.
Calculating due date for pregnancy
There are several calculation of pregnancy options:
Last Menstrual Period (LMP) - Simply enter the first day of your last menstrual period (LMP) and your cycle length and our pregnancy week calculator will let you know your due date, your current week / day and your trimester.
Conception Date - Add your conception date and the calculator will instantly show your estimated due date, current week of pregnancy and trimester.
Ultrasound Date - Add the date you had your ultrasound scan and the number of weeks and days it showed to calculate the baby's due date.
IVF Pregnancy Calculator - Select this option and enter your IVF transfer date then choose either a 3 day transfer or a 5 day transfer to calculate how far along you are and when the baby is due.
Due Date - Use the pregnancy calculator to work backwards from your due date to find your conception date and how many weeks pregnant you are.
How Is a Pregnancy Due Date Calculated?
A pregnancy due date is calculated by estimating 40 weeks (280 days) from the first day of your last menstrual period (LMP). This method assumes a regular 28‑day cycle and is the standard approach used by healthcare providers. If your cycle length is longer or shorter, your estimated due date may change slightly - you can adjust your cycle length in our calculator to account for this. Our due date calculator takes your input - whether LMP, conception date, ultrasound data, or IVF transfer date - and provides a personalised estimate of your current pregnancy week, days, and trimester.
How Many Weeks Pregnant Am I?
Understanding how many weeks along you are is one of the most common pregnancy questions. Pregnancy is measured in weeks from the first day of your last menstrual period, even though conception usually happens about two weeks later. Our pregnancy week calculator shows your weeks and days of pregnancy based on the dates you enter.
Why Pregnancy Is Measured From the Last Menstrual Period (LMP)
Pregnancy dating starts from the first day of your LMP because the exact date of conception can be hard to pinpoint. Counting from LMP gives a standardised starting point that doctors and pregnancy tools use worldwide. For those with irregular cycles, ultrasound dating often gives a more accurate estimate later in pregnancy.
Pregnancy Trimesters Explained
Pregnancy is divided into three trimesters:
- First Trimester: Weeks 4-12
- Second Trimester: Weeks 13-27
- Third Trimester: Weeks 28-40
Each trimester has unique milestones, from early embryo development in the first trimester to baby growth and movement in the second, and final preparation for birth in the third.
How Accurate Is a Pregnancy Due Date?
Estimated due dates are just that - estimates. Less than 5 % of babies are actually born on their due date. Factors like cycle length, ovulation timing, and ultrasound dating can shift your estimated arrival date. An early ultrasound (especially before 13 weeks) often refines your due date more accurately than LMP alone.
