How do I use the Ovulation Calculator?

Enter the first day of your last menstrual period. Set your average cycle length (typically 28 days). Adjust the luteal phase length if you know it (default 14 days). Click Calculate Ovulation to see your results. Review your fertile window, ovulation date, and cycle forecast.

Is the Ovulation Calculator free?

Yes, the Ovulation Calculator is completely free. It runs entirely in your browser with no signup, no download, and no data sent to any server.

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Ovulation Calculator

Estimate your fertile window and ovulation date based on menstrual cycle length. Includes 3-cycle forecast and timeline.

ovulation calculatorfertility calculatorfertile windowovulation tracker

Ovulation Calculator

Estimate your fertile window and ovulation date based on your menstrual cycle. For informational purposes only — not medical advice.

First Day of Last Period

Average Cycle Length (days)

Typical range: 21–35 days

Average Luteal Phase (days)

Usually 14 days (10–16 range)

How to use

How to Use the Ovulation Calculator

1 Enter the first day of your last menstrual period.
2 Set your average cycle length (typically 28 days).
3 Adjust the luteal phase length if you know it (default 14 days).
4 Click Calculate Ovulation to see your results.
5 Review your fertile window, ovulation date, and cycle forecast.

The Ovulation Calculator estimates when you ovulate based on your menstrual cycle. Ovulation typically occurs 14 days before your next period (the luteal phase). Your fertile window spans about 5 days before ovulation through 1 day after, as sperm can survive up to 5 days.

This calculator provides estimates based on average cycle data. Cycles can vary in length and timing. For the most accurate tracking, combine this calculator with other methods like basal body temperature monitoring or ovulation predictor kits. This tool is for informational purposes only.

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