Enter values and select Calculate to see your result.
Estimate conception timing from a pregnancy due date
Conception is estimated 266 days before the due date. Actual ovulation varies; this cannot establish an exact conception date or paternity.
How to use the Pregnancy Conception Calculator
Estimate conception timing from an estimated due date using the common 266-day assumption.
- Enter estimated due date.
- Calculate the estimated conception date.
- Use it as planning context, not an exact biological date.
Pregnancy Conception Calculator formula
Estimated conception date = due date − 266 days.
Worked example
Inputs: Estimated due date October 8, 2026.
What to expect: Estimated conception date is about January 15, 2026.
How to read your result
Ovulation and implantation vary, so this cannot establish exact timing or paternity.
Frequently asked questions
Can it identify exact conception?
No. It provides an average-based estimate.
What if due date came from ultrasound?
Use the clinician's estimate, but conception still has a possible date range.