How accurate is a due date?
Only about 4% of babies arrive on the exact date. Around 80% of births happen between 37 and 41 weeks, so treat the date as the centre of a three-week window.
Calculate your estimated due date, current trimester, and days remaining based on your last menstrual period or conception date.
Due date = first day of last period + 280 days (adjust ±(cycle length − 28) days). Gestational age = days since LMP ÷ 7. Conception ≈ LMP + 14 days.
With a last period starting 1 March and a 28-day cycle, the due date is about 6 December. On 1 August you would be roughly 22 weeks along, in the second trimester.
Only about 4% of babies arrive on the exact date. Around 80% of births happen between 37 and 41 weeks, so treat the date as the centre of a three-week window.
Add or subtract the difference. A 32-day cycle means you likely ovulated four days later, so the due date shifts four days later than the standard calculation.
Yes. A first-trimester dating scan (8–13 weeks) is accurate to within about five days and overrides an LMP-based estimate, especially with irregular cycles.