Ovulation Calculator
Track your fertility window and ovulation dates accurately. Plan pregnancy or avoid conception with our free ovulation calendar.
Average is 28 days
Fertility Calendar
On short cycles the fertile window opens before the bleeding ends. Days that are both keep the period colour and carry a pink outline, and they are part of the fertile window shown above.
Upcoming Cycles
| Cycle | Period Start Date | Fertile Window | Ovulation |
|---|---|---|---|
Export these dates
Creates the fertile days, ovulation and period dates of the next six cycles as a file for Google Calendar, Apple Calendar or Outlook. The file is built in your browser.
Copied
Copy failed. Select the result and copy it manually.
About Ovulation Calculator
The Ovulation Calculator is a free online wellness tool that helps you take informed decisions about your health. Track your fertility window and ovulation dates accurately. Plan pregnancy or avoid conception with our free ovulation calendar. This Ovulation Calculator uses research-backed formulas and clear explanations so you can understand the numbers behind your health goals. Everything runs in your browser — your personal data never touches our servers, keeping sensitive information private. Use it to track progress, plan changes, or share results with your doctor or coach.
Use Cases
How to use
Set First Day of Last Period using the date input at the top left.
Drag the Cycle Length slider between 21 and 35 days; the average is 28 days and the value shows beside the slider.
Read Most Fertile Days on the pink card together with the Estimated Ovulation date.
Use the Fertility Calendar grid to see period days, fertile window and ovulation day colour coded, with today ringed in blue.
Check the Next Period, Fertile Start, Ovulation and Fertile End tiles, then the Upcoming Cycles table for the next six predicted cycles.
Use Export calendar (.ics) to download the dates of the next six cycles into your calendar app, or Download CSV to open the same table in a spreadsheet.
Pro Tips
- Measure yourself at the same time of day for consistency — small daily variations can skew the Ovulation Calculator result.
- Round inputs conservatively — being too optimistic on numbers usually leads to unrealistic goals.
- Track results over weeks, not days. The Ovulation Calculator output becomes more meaningful as a trend.
- Discuss significant changes with a healthcare professional. The Ovulation Calculator provides estimates, not medical advice.
- Combine the Ovulation Calculator with complementary tools (water intake, sleep, calorie tracking) for a fuller picture of your health.
Frequently Asked Questions
No. The Ovulation Calculator is an educational tool. For clinical decisions, always consult a qualified healthcare provider.
No. The Ovulation Calculator runs in your browser, and your health data never leaves your device. We do not log or store any personal information.
The Ovulation Calculator uses peer-reviewed formulas and returns mathematically correct results for the inputs provided. Real-world accuracy depends on how precisely you measure your inputs.
No. The Ovulation Calculator provides estimates and general guidance only. Diagnosis requires a trained medical professional.
Yes. The interface is fully responsive and works on iOS and Android phones and tablets.
No. The Ovulation Calculator is free to use as often as you like, with no signup, ads on results, or watermarks.