Ovulation calculator

Frequently asked questions

How does the calculator estimate ovulation?

It projects the next expected cycle start by adding your cycle length to your last menstrual period date, then counts back 14 days from that projected start. That 14-day figure represents the typical luteal phase length, though it varies from person to person.

What is the fertile window and why does it span several days?

The fertile window shown runs from five days before the estimated ovulation date through one day after it. Sperm can survive in the reproductive tract for several days, so conception is possible from intercourse before ovulation actually occurs.

Will this work if my cycles are irregular?

The estimate is most reliable when your cycle length is fairly consistent. With irregular cycles, the gap between your shortest and longest cycles can shift the ovulation window by several days in either direction, making the output a rough guide rather than a reliable prediction.

Is this a substitute for clinical fertility testing?

No. Cycle-based estimates are educational tools. For conception planning or fertility concerns, tests such as ovulation predictor kits or hormone monitoring provide more direct evidence of actual ovulation timing.