Pregnancy Due-Date Calculator — Ireland

Naegele's rule

The classic estimate adds 280 days (40 weeks) to the first day of your last period. We adjust for cycle length (so a 32-day cycle ovulates later, pushing the date later).

Confirming the date

The most accurate dating comes from a first-trimester ultrasound (8–14 weeks) — it can be ±5 days. Later scans become less accurate for dating.

Important next steps

If you have just confirmed pregnancy, contact your usual treating doctor or maternity hospital — early antenatal review, folic acid, and a booking visit are important.

Frequently asked questions