justyourcalculatorPregnancy Conception Calculator
Estimate when conception happened from your due date, last period or ultrasound.
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Pregnancy Conception Calculator
When you likely conceived
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How the pregnancy conception calculator works
Conception usually happens around ovulation, roughly 14 days after the first day of the last period in a 28-day cycle (days 11 to 21 across normal cycles). Working back from a due date, conception is about 266 days (38 weeks) earlier.
Because sperm can survive up to 5 days and an egg about 12 to 24 hours, the intercourse that led to pregnancy most likely happened in the 5 days before ovulation or the day after.
Using and checking your result
Published by JustYourCalculator. Check the units and assumptions above, and compare a known example before relying on the output. Calculations use browser arithmetic and may round displayed values.
This tool provides an estimate, not a diagnosis, treatment plan or individualized medical advice. Population formulas may not fit children, pregnancy, athletes or people with health conditions. Discuss health decisions with a qualified clinician.
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