Due date and pregnancy week calculator
PARENT LIBRARY / TOOLS
Your journey to that first meeting.
Check your estimated due date, gestational age and trimester. Then find checklists to help you prepare.
An illustrative photograph generated using AI.
Calculate your result
Your result
Estimated due date
Your due date has passed. Agree your ongoing care plan with your maternity team.
This is an estimate, not a promise of a particular birth date. Gestational age means completed weeks and additional days, not time since conception.
How do we calculate?
For a 28-day cycle, we add 280 days to the first day of your last period. For other cycle lengths, we apply a simplified adjustment for the difference from 28 days. Gestational age follows the selected due date and today's date.
When should I use an agreed due date?
Use the date confirmed by your maternity team if you have one. If your period date is uncertain, cycles are irregular or your pregnancy follows IVF, agree the date with a specialist. An early pregnancy ultrasound helps establish gestational age. The calculator does not change your care advice.
ACOG convention: first trimester through 13+6, second from 14+0 to 27+6, third from 28+0. Other resources may use different boundaries.