Ovulation Calculator
Get an estimated fertile window and ovulation date as you type.
FREE - NO SIGN-UP - RUNS ON YOUR DEVICE
Your entries stay on your device
- Liveupdates as you type
- 0data uploaded
- 1clear result
- Freeno account needed
Ovulation Calculator at a glance
- Input
- Enter the first day of the last period a
- Output
- an estimated fertile window and ovulatio
- Health notice
- Estimate, not medical advice
- Processing
- Runs locally in your browser
- Price
- Free
- Account required
- No
How to use Ovulation Calculator
- 1
Enter your values
Enter the first day of the last period and cycle length.
- 2
Review the estimate
Review the live estimate.
- 3
Copy the result
Copy the result when ready.
Frequently asked questions
Is this result medical advice?
No. It is a general estimate based on the values and formula shown. A qualified health professional can interpret measurements for your circumstances.
Are my entries uploaded?
No. The calculation runs in your current browser tab, and the tool does not send the values to a server.
Why might my result differ elsewhere?
Methods, rounding and reference assumptions vary. Check the selected units and inputs, then treat the result as an estimate rather than a diagnosis.
Understanding the estimate
Enter the first day of the last period and cycle length. See estimated ovulation, fertile window and next period dates. This calculator provides an estimate, not medical advice.
- The result follows the method named in the tool and rounds figures for easy reading.
- Personal circumstances vary, so use the figure as a general reference and not a diagnosis.
Full specification
| Input | Enter the first day of the last period and cycle length. |
|---|---|
| Output | See estimated ovulation, fertile window and next period dates. |
| Health notice | This result is an estimate for general information and is not medical advice. |
| Processing | All calculations run locally in the current browser tab. |
| Price | Free |
| Account required | No |
Keep going with the same files
All health tools: Health tools on SPOTTOOLS