Conception Calculator

Estimate your conception date from the first day of your last menstrual period.

Enter the first day of your last menstrual period to estimate your conception date.

First day of last menstrual period *

Your result

15-06-2026

Estimated conception date

Conception window (start)12-06-2026

Conception window (end)18-06-2026

AI explanation

Estimated conception = last period date + 14 days, assuming a standard 28-day cycle

LMP 2026-01-01

Worked example: LMP 2026-01-01
Field	Value
First day of last menstrual period	01-01-2026
Estimated conception date	15-01-2026

Assumes ovulation (and conception) occurs around day 14 of a standard 28-day cycle.
The conception window spans a few days either side of the estimated ovulation date.
Informational only.

How is conception date estimated?

Assuming a standard 28-day cycle, ovulation (and likely conception) occurs around day 14 after the start of the last menstrual period.

Can this tell me the exact day I conceived?

No — it's an estimate based on average cycle timing. Actual ovulation can shift earlier or later depending on your individual cycle length.

How does this relate to my due date?

Your due date (Naegele's rule) is set at 280 days from your last period, which works out to about 266 days after this estimated conception date.

Methods for Estimating the Due Date — American College of Obstetricians and Gynecologists (ACOG). Effective 01-05-2017, reviewed 13-09-2026.

This calculator provides a general estimate only and does not constitute personalized medical advice.