How to use the Pregnancy Conception Calculator
Work backward to an estimated conception date from a due date, period, ultrasound, or IVF transfer. It includes Due date, Last menstrual period, Ultrasound, IVF transfer workflows, so choose the one that matches the values you actually know. Use it to understand an educational estimate and the inputs behind it, not as a diagnosis or treatment decision.
Step by step
- For the Pregnancy Conception, enter your due date, first day of your last period, average length of your cycles, ultrasound date, ultrasound week. Keep each value in the unit displayed beside its field.
- Review the selected Pregnancy Conception workflow and inputs, then read estimated conception date in the result panel.
- Change one Pregnancy Conception assumption at a time to compare scenarios. Use Reset to restore this tool's worked example values.
How the calculation works
Estimated conception is 266 days before due date or 14 days after the cycle-adjusted gestational start.
Worked example
In the Pregnancy Conception worked example, your due date 2026-10-08, first day of your last period 2026-01-01, average length of your cycles 28 days, ultrasound date 2026-03-26 produces estimated conception date of January 15, 2026. Based on the due date. Review the displayed units before comparing the result.
Understanding the result
The Pregnancy Conception reports estimated conception date. Use it to understand an educational estimate and the inputs behind it, not as a diagnosis or treatment decision. Educational estimate only; it cannot diagnose a condition or replace advice from a qualified health professional.
How to check the answer
Check the Pregnancy Conception estimate by confirming the units and supported ranges for your due date, first day of your last period, average length of your cycles. Compare estimated conception date with another published method or direct measurement when available, and ask a clinician before using it for a health decision.
Common questions
What does the Pregnancy Conception calculate?
Work backward to an estimated conception date from a due date, period, ultrasound, or IVF transfer.
Which Pregnancy Conception inputs have the biggest effect?
estimated conception date responds directly to your due date, first day of your last period, average length of your cycles, ultrasound date, ultrasound week. Change one input while holding the others constant to see its effect.
Is the Pregnancy Conception result exact?
Educational estimate only; it cannot diagnose a condition or replace advice from a qualified health professional. Recheck your due date, first day of your last period, average length of your cycles and use estimated conception date only for a decision where that level of precision is appropriate.