Ovulation Calculator
Estimate when you are most likely to ovulate based on your cycle length and last period, including the most fertile window.
Scan to open on your phone
Point your phone camera at the code to open this tool.
Estimate when you are most likely to ovulate based on your cycle length and last period, including the most fertile window.
How to use Ovulation Calculator
- Open the toolNo signup and nothing to install; it works as soon as the page loads.
- Set “First day of last period”
- Set “Cycle length (days)”
- Read the resultChange any input and the result is recalculated immediately.
Nothing you enter leaves your device
All of the work happens inside your browser. Whatever you type is never packaged up and sent to a server, and no request this page makes carries it.
That makes it safe for contract amounts, personal details and internal documents you would rather not hand to a third party — close the tab and it is gone.
What this tool does not do
Ovulation Calculator only does what a browser can do on its own — it talks to no backend service. So it keeps no history for you and syncs nothing across devices; if you need a record, copy or download the result.
It is also not a substitute for professional judgement. For legal, medical or tax decisions, treat the output as a starting point rather than a final answer.
Frequently Asked Questions
- How accurate is this?
- The estimate is reliable if your cycle is regular to within a day or two. If your cycle varies a lot month to month, ovulation is also shifting, so use this as a guide.