HEALTH REFERENCES WITH CLEAR LIMITS
Pregnancy Due Date Calculator
Estimate a due date by adding 280 days to the first day of the last menstrual period.
Review your result
Your result
Ready when you are.
Enter your values and select Calculate. Your result stays on this device.
How it works
Estimated due date = first day of the last menstrual period + 280 days.
Assumptions
This convention assumes a regular 28-day cycle. An early ultrasound or clinician may change the estimated date.
Use case
pregnancy calculator: a clear planning check
Estimate a due date by adding 280 days to the first day of the last menstrual period. The stated formula, assumptions, and result limits remain visible so the calculation can be checked in context.
Use a clear pregnancy calculator scenario with values you can verify before relying on the result.
Source and update
Last reviewed: 2026-08-10
ACOG — methods for estimating the due dateKeep exploring