Estimated Conception Date
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Estimated Last Period
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Free Pregnancy Conception Calculator
Estimate your conception date from your due date.
This reverses Naegele's rule: due date minus 266 days gives an estimated conception date, and due date minus 280 days gives an estimated LMP date. These are estimates — actual conception can occur within a several-day fertile window, not on one exact day.
Frequently Asked Questions
Is this an exact conception date?
No — conception typically occurs within a several-day fertile window, so treat this as an estimate centered on the most likely date.