Pregnancy Due Date Calculator
Calculate your estimated due date, current week, and trimester from your last menstrual period or conception date.
Select the relevant date based on your chosen method
Only used for LMP method — standard is 28 days
How It Works
For the LMP method, the calculator adds 280 days to your last period date, adjusting for cycle lengths other than 28 days. For conception date, it adds 266 days. For IVF, it adds 266 days minus the embryo age (3 or 5 days). It shows your estimated due date, current gestational week, trimester, and days remaining.
Frequently Asked Questions
How is the due date calculated?
Using Naegele's Rule: add 280 days (40 weeks) from the first day of your last menstrual period (LMP). If your cycle is longer or shorter than 28 days, the calculation adjusts by the difference. Only about 5% of babies arrive on their exact due date — most arrive within 2 weeks either side.
When are the trimesters?
First trimester: weeks 1-12. Second trimester: weeks 13-27. Third trimester: weeks 28-40. Key milestones include the first ultrasound around 12 weeks, anatomy scan at 18-20 weeks, and viability at 24 weeks.
When should I have my first prenatal appointment in Australia?
Book your first appointment with a GP or midwife as soon as your pregnancy is confirmed, ideally before 10 weeks. Your first hospital booking appointment is usually around 12-16 weeks. Medicare covers most prenatal care in the public system.
What are the key dates in an Australian pregnancy?
12-week scan (nuchal translucency), 18-20 week anatomy scan, 24-28 week glucose tolerance test, 36-week Group B Strep test, and weekly appointments from 36 weeks. Paid Parental Leave (government) requires lodging a claim with Services Australia before the birth.
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