Free Period Tracker & Ovulation Calendar Online
Track your menstrual cycle, predict your next period and fertile window — no app download, no sign-up, no data ever sent to a server.
Track My Cycle →Everything You Need to Track Your Cycle
One free tool — period prediction, ovulation tracking, cycle history, and PDF export.
Personalised Menstrual Calendar
See your next 12 months of predicted periods, fertile windows, and ovulation days at a glance — colour-coded by flow intensity.
Ovulation & Fertile Window Prediction
Get scientifically-calculated ovulation dates and your 6-day fertile window — useful for natural family planning or understanding your cycle.
PDF Export & Print-Ready Calendar
Download your calendar as a PDF or print it directly. Perfect for offline records or sharing with your healthcare provider.
100% Private — No Server Storage
Unlike apps that upload your health data, everything stays in your browser's local storage. No account, no cloud sync, no privacy risk.
Cycle History & Smart Insights
Log multiple periods to build your history. The tracker auto-calculates your real average cycle length for increasingly accurate predictions.
Start Tracking Your Cycle
Enter your last period details to generate a personalised 12-month calendar.
How Our Period Tracker Works — and Why It's Different
Most period tracker apps require you to create an account, upload your health data to their servers, and accept privacy policies that allow your most intimate health information to be used for targeted advertising. This tracker works differently: your data never leaves your browser.
The cycle prediction algorithm explained
The calendar uses the standard clinical prediction method. Ovulation is estimated to occur approximately 14 days before your next expected period — which means the formula is: Last Period Date + (Cycle Length − 14) = Predicted Ovulation Day. For a 28-day cycle that started on 1 June, ovulation would be predicted around 14 June.
The fertile window is the six-day window ending on ovulation day: the five days before ovulation (when sperm can survive in the fallopian tubes) plus the ovulation day itself (when the egg is released and viable for 12–24 hours). This six-day window is the only time in each cycle when pregnancy is possible.
The more cycles you log in the history section, the more accurate your predictions become. When you have at least two logged periods, the tracker automatically calculates your real average cycle length instead of relying on the default 28-day assumption.
Complete privacy — your data stays in your browser
Everything you enter is stored in your browser's localStorage — a private storage area that stays on your device. Nothing is transmitted to our servers. There is no account, no login, and no way for us (or anyone else) to access your cycle data.
This matters. Period data is among the most sensitive health information a person can share. Since 2022, there has been increasing legal and social scrutiny of period apps that store data in the cloud, particularly in jurisdictions where reproductive health decisions can have legal consequences. This tracker was designed from the start with a local-only approach.
Important: Your data is tied to your browser and device. Clearing your browser's site data or using a different browser will erase your history. If you want a permanent record, use the Print or PDF export button to save your calendar.
Who this tracker is designed for
This tool is useful for anyone who wants to understand their cycle without downloading an app or creating an account. It works well for people with relatively regular cycles (varying by fewer than 7 days each month). For those with highly irregular cycles, polycystic ovary syndrome (PCOS), or perimenopause, predictions will be less reliable — the tracker can still log your history, but predictions should be taken as rough estimates.
If you are trying to conceive, the fertile window prediction here is a starting point, not a comprehensive fertility assessment. Tracking additional fertility signs — such as basal body temperature (BBT) and cervical mucus changes — significantly improves accuracy.
Understanding your menstrual cycle phases
Your cycle has four phases. The menstrual phase (days 1–5 on average) is when bleeding occurs as the uterine lining sheds. The follicular phase (days 1–13) overlaps with menstruation and ends at ovulation — oestrogen rises and a follicle matures in the ovary. The ovulation phase (around day 14 in a 28-day cycle) is the brief window when the egg is released. The luteal phase (days 15–28) follows ovulation — progesterone rises to prepare the uterine lining, and falls again if implantation does not occur, triggering the next period. Read more in our complete guide to menstrual cycle phases.
When a late or irregular period warrants medical attention
Occasional variation of a few days is completely normal. Cycles can shift due to stress, illness, travel, significant weight changes, or intense exercise. However, you should speak with a healthcare provider if:
- Your period is more than 7 days late and a pregnancy test is negative
- You have fewer than 8 periods per year (oligomenorrhea)
- Your periods have stopped entirely for 3+ months (amenorrhea) and you are not pregnant or postmenopausal
- Your cycle regularly varies by more than 9 days
- You experience severe pain (dysmenorrhea) that disrupts daily activities
See our guide on irregular periods and their causes and our guide on reasons your period may be late for more detail.
Other free tools on this site
Beyond the period tracker, we offer a standalone ovulation calculator, a pregnancy due date calculator, an implantation date calculator, and a next period calculator. All tools are free, require no sign-up, and store no data on any server.
Frequently Asked Questions
How accurate is this period tracker?
Our tracker uses the standard cycle prediction algorithm: ovulation is estimated at cycle length minus 14 days from your last period. Accuracy improves with more cycles logged — it works best for cycles of 21–35 days. It is a planning guide, not a medical device.
Is my period data private and secure?
Yes. All your cycle data is stored exclusively in your browser's localStorage. It is never sent to any server, never shared with third parties, and never used for any purpose beyond showing your calendar. Clearing your browser data will erase it.
Do I need to create an account or sign up?
No. This period tracker requires no sign-up, no email address, and no account of any kind. Just enter your last period date and cycle length and your calendar is ready instantly.
How does the ovulation and fertile window prediction work?
Ovulation is predicted at day (cycle length − 14) of your cycle. The fertile window spans the 5 days before ovulation plus the ovulation day — the period when conception is most likely. These are statistical estimates; actual ovulation varies by person and cycle.
Can I use this tracker for irregular periods?
Yes, within limits. Log multiple periods over time and the tracker will automatically recalculate your average cycle length from your history. However, if your cycles vary by more than 7–9 days each month, predictions will be less precise. See our irregular periods guide.
Can I edit or delete period entries?
Yes. After generating your calendar, a Period History section appears below it. You can add new periods, edit existing entries (start date, duration, flow intensity), or delete any record using the edit and delete buttons next to each entry.
How do I print or download my period calendar as a PDF?
After generating your calendar, click Print Calendar to open your browser's print dialog. Click Download PDF to use the same dialog with your printer set to "Save as PDF". The layout is optimised for A4 and US Letter paper.
Does this period tracker work on mobile phones?
Yes. The tracker is fully responsive and works on any device — phone, tablet, or desktop — in any modern browser without needing to download an app.
What should I do if my period is very late or I have irregular cycles?
If your period is more than 7 days late and a pregnancy test is negative, consult a healthcare provider. Common causes include stress, weight changes, intense exercise, thyroid disorders, and PCOS. See our guide on late period reasons.
Is this a free period tracker with no hidden costs?
The tracker is completely free to use with no subscription or sign-up. The site displays third-party display ads to cover hosting costs. These ads do not access your cycle data, which remains in your local browser storage only.