Track your period online without an app or account. Enter your last period date and cycle length to predict your next period, ovulation day, and fertile window in seconds.
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Online tracking beats pen-and-paper for one simple reason: the math is done for you. Here's what a good tracker can do.
Once you know your average cycle length, your next period is a simple addition. The tracker does it instantly and shows you ovulation too — the 6-day window when pregnancy is possible.
Consistent tracking helps you notice when cycles shift by 7–9+ days. That pattern can be an early signal worth discussing with a doctor.
Trips, exams, swims, events — knowing your likely period dates helps you pack and plan with confidence instead of being caught off guard.
Many apps collect and sell health data. Our tracker runs in your browser — nothing is stored on any server, and there is no sign-up to track you.
Note: Cycle predictions are estimates based on averages and work best for regular cycles (21–35 days). They are not a form of birth control and do not replace medical advice.
Ovulation typically happens about 14 days before your next period. Here's how common cycle lengths map out:
| Cycle Length | Ovulation Day | Fertile Window |
|---|---|---|
| 21 days | Day 7 | Days 2–7 |
| 25 days | Day 11 | Days 6–11 |
| 28 days | Day 14 | Days 9–14 |
| 32 days | Day 18 | Days 13–18 |
| 35 days | Day 21 | Days 16–21 |
Your cycle length = the number of days from the first day of one period to the first day of the next.
It uses your last period date and average cycle length to predict future period dates. Ovulation is estimated as roughly 14 days before your next period. All calculations run locally in your browser.
Most accurate for regular cycles (21–35 days). Results are estimates, so track 3–6 cycles and update your average length. Stress, illness and lifestyle changes can shift ovulation timing.
No. No account, no email, no download. Your data never leaves your device.
If cycles vary by more than 7–9 days, predictions are less reliable. Track every start date for a few months, and see a doctor if periods are often unpredictable or you miss 3+ periods in a row.
No. Cycle tracking is not a reliable contraceptive method. Sperm can survive up to 5 days, so pregnancy is possible outside the estimated fertile window. Consult a healthcare provider for family planning.