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Interactive Ovulation Calculator

Health

Estimate your fertile window and next ovulation dates.

ttb run ovulation-calculator

Typical cycle length is 21-35 days. Average is 28 days.

Ovulation Date
Thu, May 21
in 14 days
Fertile Window
May 16 to May 22
Next Period
Jun 4
Cycle Length
28 days
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How to Use Ovulation Calculator

Enter the first day of your last period and your average cycle length. The calculator estimates your ovulation date and fertile window (the 5 days before ovulation plus ovulation day). All data is processed locally and never sent to any server. Color-coded calendar view makes tracking easy.

1

Enter your parameters

Configure the inputs for the Ovulation Calculator according to your specific needs.

2

View real-time results

The utility instantly processes your request and displays the calculated outputs directly in your browser.

3

Copy or Download

Click the copy icon next to the final output to instantly grab the result, or export it if applicable.

Frequently Asked Questions

When does ovulation occur?+
Ovulation typically occurs 12-16 days before the start of your next period (not 14 days after your last period). For a 28-day cycle, that's around day 14. For a 32-day cycle, it would be around day 18.
How long is the fertile window?+
Sperm can survive up to 5 days in the reproductive tract, and an egg lives for 12-24 hours after release. This creates a fertile window of approximately 6 days: the 5 days before ovulation through the day of ovulation.

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