The standard Naegele's rule adds 280 days (40 weeks) to the first day of the last menstrual period, assuming a 28-day cycle. Ultrasound dating can move the estimate, and only a clinician can confirm it — treat this as a planning aid, not medical advice.
Only about 4–5% of babies arrive on the exact date; most come within two weeks either side.
Add or subtract the difference from 28 days to the result, or ask your clinician for an ultrasound-based date.
No — it is an estimate for planning. Confirm all dates with your healthcare provider.
Other calculators and planners on timedatelive.