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Period & Ovulation Calculator

Next period date, ovulation day, and fertile window — 3-month forecast

Last Period Start Date

Cycle Length (days)

Period Duration (days)

Next Period Date

Ovulation Date

Fertile Window

Relatively Safe Period (est.)

📅 3-Month Forecast

#	Period Date	Ovulation	Fertile Window

⚠️ This tool is for informational purposes only and should not be used as a medical diagnosis or contraception method. Consult a healthcare professional for accurate guidance.

💡 Tips

Ovulation is estimated as cycle length − 14 days (based on a fixed 14-day luteal phase)
The fertile window spans 5 days before ovulation to 1 day after, when conception is most likely
Irregular cycles can cause larger prediction errors — use average cycle length from recent months

Frequently Asked Questions

How is ovulation date calculated?

The luteal phase (ovulation to next period) is typically a fixed 14 days. So ovulation = next period date − 14 days. Cycle length affects when ovulation occurs relative to the last period.

Can I use this if my cycle is irregular?

You can use an average of your recent cycles as input, but predictions will be less accurate. For irregular cycles, we recommend consulting a doctor or using a dedicated period-tracking app.

Is my data saved anywhere?

No. All calculations run entirely in your browser. No data is sent to any server.

Period & Ovulation Calculator

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💡 Tips

Frequently Asked Questions