Free · Browser-Based · Cycle Planning

Ovulation Calculator

Estimate the fertile window, likely ovulation day, and next period date using your cycle length and the first day of your last period.

First day of last period

Cycle length (days)

Luteal phase (days)

Planning mode

Cycle summary

🎯 Common Use Cases

Predict fertile days

Estimate ovulation timing

Project next period date

Review cycle timeline quickly

Is this exact?

No. It is only a cycle-based estimate and may not match real ovulation timing exactly.

Can I change cycle length?

Yes. Enter your typical cycle and luteal phase length to shift the estimate.

Does it run locally?

Yes. Your dates stay in the browser.