Calculate your current pregnancy week, trimester and key milestones from your LMP date.
Finding out you're pregnant and immediately trying to work out your due date is practically universal — and this calculator gives you the answer along with where you are in your pregnancy in weeks and days, your estimated conception date, and the key trimester milestones.
Due dates are calculated from the first day of your last menstrual period (LMP) using the standard 280-day / 40-week rule, which assumes a 28-day cycle with ovulation at day 14. If your cycles are longer or shorter, your actual due date may differ slightly — your OB or midwife will confirm with an early ultrasound, which is the most accurate method.
Only about 5% of babies arrive on their exact due date. The EDD (estimated due date) is the midpoint of a window — full-term births typically happen anywhere between 37 and 42 weeks. What the date really gives you is a planning anchor.
Calculated due dates based on LMP are a starting point — accurate to within a week or two for most people with regular cycles. An early ultrasound (ideally before 14 weeks) is significantly more accurate and will be used by your care provider as the reference date.
First trimester: weeks 1-12. Second trimester: weeks 13-26. Third trimester: weeks 27-40. Some definitions vary slightly, but this is the most commonly used breakdown in Australian obstetric practice.
You can still calculate an estimate, but irregular cycles mean the standard LMP method may be less accurate. An early dating ultrasound is especially important if your cycles vary significantly in length.
Gestational age is how far along the pregnancy is, measured in weeks from the first day of the last menstrual period — not from conception. This is the standard measurement used by OBs and midwives in Australia.