Pregnancy due date estimate
Estimate a due date from the first day of the last period.
How this works
Naegele’s rule adds 280 days (40 weeks) to the first day of the last period.
Example
Using the example inputs, estimated due date is Jul 8, 2027.
- First day of last period
- 2026-10-01
- Estimated due date
- Jul 8, 2027
Your clinician or dating ultrasound may revise this estimate.
Scope and assumptions
Educational estimate, not confirmation of pregnancy or clinical dating. Assumes a regular 28-day cycle.