Conception Calculator
Estimate when conception occurred based on your due date.
Conception Calculator
Private Period & Cycle Tracker
Cycle, Ovulation & Fertility
How to calculate conception date
Estimate when you conceived based on your expected due date or last menstrual period.
1
Due date
Conception usually happens about 38 weeks before the due date.
2
Calculation
We subtract 266 days from your due date to find the probable conception window.
3
Accuracy
This is an estimate, as ultrasound measurements provide the most accurate dating.
Common Questions
Why use due date instead of last period?
If your cycles are irregular, an ultrasound-based due date is more accurate for finding conception.
Can I know the exact day?
Sperm can live up to 5 days, so conception is usually a window rather than a single day.
Steps For
PregnancyMothers to beUltrasound dating