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Conception Date Calculator

Estimate your approximate conception date based on your last menstrual period or your estimated due date.

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First Day of Last Period

Estimated Conception

Approximate Conception Date

This is a rough estimate only. Actual conception can vary by several days depending on individual cycle length and ovulation timing.

This is an estimate for informational purposes only and is not medical advice. Consult a healthcare provider.

How to Calculate & Formula Details

Mathematical Model FormulaFrom LMP: Conception date = Last period start date + 14 days. From due date: Conception date = Due date - 266 days.

This calculator provides a rough estimate of when conception likely occurred, using either the first day of your last menstrual period (LMP) or your estimated due date as a starting point.

Why This Is an Estimate

Conception typically occurs around ovulation, roughly 14 days after the start of a period in an average 28-day cycle. Since actual ovulation timing varies by individual and cycle length, the true conception date can differ from this estimate by several days.

Frequently Asked Questions

How is conception date different from due date?

Due dates are typically calculated as 280 days (40 weeks) from the last menstrual period, while conception usually occurs about 2 weeks into that cycle, roughly 266 days before the due date.

Can this tell me the exact date I conceived?

No. This is a statistical estimate based on average cycle timing. Only a fertility specialist tracking ovulation directly, such as through an IVF cycle, can pinpoint an exact conception date.

What if I have an irregular cycle?

Irregular cycles make this estimate less reliable, since ovulation timing is harder to predict. An early ultrasound during pregnancy can give a more accurate gestational age estimate.

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