Conception Date Calculator
Estimate conception date, due date, and pregnancy progress using either due date or LMP.
Use this Conception Date Calculator to estimate conception date, due date, ovulation timing, and pregnancy progress from a due date, known conception date, or the first day of the last menstrual period (LMP).
Calculation Methods
If the due date is known:
Estimated conception date = due date − 266 days
If the conception date is known:
Estimated due date = conception date + 266 days
For a regular 28-day cycle:
Estimated due date = LMP + 280 days
For other regular cycle lengths:
Adjusted due date = LMP + 280 days + (cycle length − 28 days)
Approximate ovulation can be estimated as:
Ovulation ≈ LMP + (cycle length − 14) days
Example
If the estimated conception date is January 1, 2026:
January 1 + 266 days = September 24, 2026
The estimated due date is therefore approximately September 24, 2026.
Important Note
Calendar calculations provide estimates only. Ovulation and conception do not always occur on the expected day, particularly with irregular cycles.
First-trimester ultrasound is generally more accurate for establishing or confirming gestational age than calendar estimates alone. Pregnancy dating used for medical care should be confirmed by a qualified healthcare professional.