The Conception Calculator

Due on St. Patrick's Day: When Did You Conceive?

Due dates & conception. Updated . Calculated with the standard pregnancy dating method used by ACOG and the NHS.

A baby due on St. Patrick's Day (March 17) was most likely conceived around June 24 of the previous year.

Due dateMarch 17
Most likely conception dateJune 24
Likely conception windowJune 21 – June 27
Estimated last periodJune 10

Only a small share of babies arrive on their exact due date, so a holiday due date is a target rather than a promise.

Use the conception date calculator for your exact dates.

Conception Date Calculator: Find the most likely conception date from your due date.

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This article is general information, not medical advice. Talk to a doctor or midwife about your own pregnancy or fertility.