How the fertile window is estimated

Ovulation typically occurs about cycle length − 14 days after the last menstrual period. The fertile window is the 5 days before ovulation plus ovulation day itself, since sperm can survive ~5 days.

Frequently Asked Questions

Is the Ovulation Calculator free to use?

Yes, the Ovulation Calculator is 100% free to use. There are no subscriptions, no sign-ups, and no hidden fees.

Is my data safe when using the Ovulation Calculator?

Absolutely. All calculations performed by the Ovulation Calculator happen locally in your web browser. We do not store, track, or transmit your inputs or results to any server.

How accurate is the Ovulation Calculator?

Our Ovulation Calculator uses industry-standard formulas and methodology. You can view the exact formula and calculation logic used in the methodology section above to verify the math yourself.

Can I use the Ovulation Calculator on my mobile phone?

Yes! The Ovulation Calculator is fully responsive and works seamlessly on all devices including smartphones, tablets, and desktop computers.