Due Date Calculator
Estimated due date, current stage and trimester dates.
An estimate. A dating ultrasound is more reliable.
How it works
Naegele's rule adds 280 days to the first day of the last menstrual period, assuming a 28-day cycle with ovulation on day 14. Longer or shorter cycles shift the date, which this adjusts for.
Only about 4% of babies arrive on the estimated date. Anything from 37 to 42 weeks is considered term. A dating scan in the first trimester is more accurate than any calculation from dates.