Free period tracker
Your next period, ovulation day and fertile window, worked out in your browser. Nothing you enter leaves your device.
Missed period
One late or skipped period is common and usually isn't a sign that something is wrong. Here's how to think about it.
General information, not medical advice. More on irregular and missed periods.
Inside the cycle
The lining built up last cycle starts to shed. Oestrogen and progesterone are at their lowest, and cramps are common as the uterus contracts.
You're on day – today.
Scroll to move through the cycle, or drag on the chart.Drag across the chart to move through the cycle.
Next period
Ovulation day
Fertile window
Cycle length
Tap any day to see what's happening.
Predictions are estimates based on the calendar method. Don't use them as contraception.How we calculate
Features
Every day of your cycle on one ring: period, follicular, fertile window and luteal, with a countdown to your next period.
Period days, fertile window and ovulation marked across the next three months. Print it for your doctor.
100%
Nothing you enter is uploaded. There's no account and no server to send it to.
Add it to your home screen and it opens like an app, even on a plane.
Next period, ovulation day, fertile window and cycle length, each with a plain date and a countdown.
How it works
01
Enter the first day of your last period and your usual cycle length. That's the whole setup.
02
Your next period, fertile window and estimated ovulation, counted down on one screen and marked on your calendar.
03
Three months on one page, and every day tells you which phase it falls in and what your body is doing.
Privacy
Most period apps keep your cycle on their servers. This one can't. It's a plain website with no database and no login, so there's nowhere for your dates to go.
Delete everything in one tap, or let it forget when you close the tab.
Yes. There's no paid version and nothing to unlock. You don't need an account, an email address or an app.
In your browser, on your device, and only while the tab is open. Close it and they're gone. They are never sent to us.
We add your cycle length to the first day of your last period to get the next one. Ovulation is estimated 14 days before that, and the fertile window runs from five days before ovulation to the day after. The methodology page has the details.
It's a calendar estimate, so treat it as a guide. Periods often come a few days early or late, and a calendar can't detect ovulation. Using your own average cycle length helps. More on accuracy.
No. Please don't use these predictions as contraception. You can get pregnant outside the estimated fertile window, and no day on the calendar is a "safe day".
Yes, but treat the dates as a wider window. Count the days between your last three periods, average them, and enter that as your cycle length. Tracking irregular periods.
Tap any day on the calendar and you'll see which phase it falls in and what's usually happening in your body that day. The Inside the cycle section shows the hormones behind it.
Yes, after your first visit. On your phone you can use Add to Home Screen in your browser's menu and open it like an app.
Close the tab. Nothing is kept after that, and we never had a copy.
Guides