About the Conception Calculator

Your most likely conception date usually falls close to ovulation, since that is when an egg is available for fertilisation.

Formula Used

Likely Conception Window = Ovulation Date - 5 days to Ovulation Date

How It Works

This calculator estimates ovulation from your last period and cycle length, and shows the surrounding window as your likely conception range.

Step by Step

Estimate your ovulation date from your last period and cycle length.
Sperm can survive up to 5 days, so the fertile window starts 5 days before ovulation.
Conception is most likely to have occurred somewhere within this window.

Worked Example

Example: Estimated ovulation on 15 January:

Conception window = 10 January to 15 January

Frequently Asked Questions

Is conception date the same as ovulation date?

They're usually very close - conception can only happen within about 24 hours of ovulation, though sperm can fertilise an egg from intercourse a few days earlier.

Why is a range given instead of one date?

Because sperm can survive in the body for up to 5 days, conception could technically result from intercourse anytime in that window before ovulation.

How reliable is this estimate?

It's a reasonable estimate for regular cycles, but actual ovulation timing can vary from month to month.

CALCULATOR EXPERT

Conception Calculator