Log period start dates and length, see your cycle history, and get a simple estimate of your next date — clearly labelled as an estimate, not a prediction. Saves in your browser. Free.
| Start date | Length | Cycle length | Notes |
|---|
💾 Saves in this browser only — this is sensitive data, so make sure you're comfortable with who else uses this device. Logging and history only: no ovulation or fertility predictions, and any next-period estimate is a rough average, not medical advice.
Key takeaways:
This is a straightforward logging tool: record when a period starts and how long it lasts, and it builds a history of your cycle lengths automatically. It's deliberately kept simple — a private log and history, not a fertility app with ovulation windows or conception predictions.
Once you've logged two or more periods, an estimated next date appears, based on your average cycle length. It's a rough guide only, clearly labelled as an estimate — cycles vary naturally, and the number shouldn't be relied on for anything medical.
Ovulation and fertile-window predictions require assumptions this tool deliberately avoids making, since cycle timing varies person to person and month to month, and a wrong guess here carries real consequences. What it does instead is give you an honest, simple history: your actual logged dates, your calculated cycle lengths, and a plainly labelled estimate of your next start date based on your own average — nothing more.
If you're tracking symptoms alongside your cycle, the Mood Tracker pairs well for a fuller picture, and for anything about irregular cycles, fertility, or symptoms that concern you, a GP or gynaecologist is the right source of advice.
Does this predict ovulation or fertility?
No. This tool logs period start dates and length and shows your cycle history. It does not calculate or predict ovulation, fertile windows, or anything related to conception.
How is the estimated next period calculated?
Your last period start date plus your average cycle length from logged history. It's a simple average-based estimate, not a medical prediction, and only appears once you've logged at least two periods. Cycles vary naturally, so treat it as a rough guide, not a guarantee.
Where is my period data stored?
Entirely in this browser's local storage, on this device — nowhere else, and nothing is uploaded. This is sensitive information, so it's worth checking you're comfortable with who else uses this device.
What counts as cycle length?
The number of days between the start of one period and the start of the next. It's calculated automatically once you've logged two or more start dates.
Can I edit or delete an entry?
Delete any row with the ✕ button. There's no in-place edit — remove the entry and log it again with the correct date.
Is this medical advice?
No. This is a logging and history tool only — it doesn't diagnose irregularity or any condition. For concerns about your cycle, talk to a GP or gynaecologist.