Pregnancy due date calculator
Work out your due date from your last period, conception, IVF transfer or a dating scan.
Milestones
| Milestone | Week | Date |
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This calculator is for information only and does not replace advice from a doctor or midwife.
Questions people ask
How is the due date calculated?
By Naegele’s rule: 280 days (40 weeks) from the first day of the last period, assuming a 28-day cycle. Longer or shorter cycles shift it by the difference. From conception it is 266 days.
How accurate is a due date?
It is an estimate. Only about 4–5% of babies arrive on their due date; most come within two weeks either side. An early ultrasound, especially before 14 weeks, gives the most reliable date, and your care provider will use it if it differs.