Conception Date Calculator

Use this conception date calculator to estimate a conception date or related pregnancy date. Enter due date or last menstrual period and cycle details and review an estimated conception date and related dates.

Estimated conception date
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Fertile window (±3 days) —

An estimate based on standard obstetric convention (average 28-day cycle) — actual ovulation and conception timing varies between individuals.

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How it works

Conception ≈ LMP + 14 days (typical cycle); or due date − 266 days

How to use the Conception Date Calculator

Start by entering due date or last menstrual period and cycle details. Keep the units consistent and check that each value belongs to the same question.

The result gives an estimated conception date and related dates. Ovulation timing varies, so dates are approximate. Use it as a guide and check any instructions, rules or professional advice that apply.

Frequently Asked Questions

What does this conception date calculator calculate?
It gives an estimated conception date and related dates. Ovulation timing varies, so dates are approximate.
What information should I enter?
Enter due date or last menstrual period and cycle details. Use the same units throughout so the result is easier to understand.
Is the conception date exact?
No. It is an estimate based on the information entered.