Free cycle tool
Enter three details and see your next period date, your fertile window and your ovulation day, with a three-month calendar you can plan around.
Track your cycle, predict your fertile window and plan ahead.
Nothing is saved or sent. Your dates stay in your browser.
Your 3-month cycle calendar
Want to keep tracking your cycle?
Get our free printable cycle tracker, by email.Free printable tracker
Pop your email in and we will send you our free printable cycle tracker. Print it, stick it inside a diary, and mark your days offline. No cost, and we will not flood your inbox.
Thank you for tracking with us
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Good to know
A few things people often ask us about cycles and about this calculator.
It uses the standard calendar method. Ovulation is estimated at about 14 days before your next period, and the fertile window as the five days before ovulation plus ovulation day itself. For a fairly regular cycle it is a good guide. It cannot sense what your body is doing on a given day, so please treat it as an estimate rather than a test.
They are the days when pregnancy is possible. Sperm can survive up to about five days, and the egg lives for roughly a day after ovulation. That is why the calculator marks a window of about six days rather than a single day.
The calculator assumes your cycle stays close to the length you entered. If it varies by more than a few days from month to month, the predicted dates will move as well. Noting your actual start dates for two or three months, which is what our printable tracker is for, gives you a far better picture than any single calculation.
Please do not rely on it. This calculator is not a method of contraception. Calendar based methods have a high failure rate in ordinary use, and they are least reliable for irregular cycles, for teenagers and around menopause. For contraception, please speak to a doctor about a method that suits you.
Your expected period days, your ovulation day, your fertile window and the remaining days, for this month and the two that follow. It is a planning aid, for travel, exams, or simply knowing when to keep supplies handy.
Keep reading
Plain, practical guides written by the team that runs menstrual health sessions in government schools.
A menstrual cycle is counted from the first day of one period to the day before the next one starts. This calculator takes the first day of your last period, the usual length of your cycle and how long your period normally lasts, and works forward from there.
Your next period is estimated one cycle length after your last one began. Ovulation is estimated at about fourteen days before that next period, which is the standard calendar method. The fertile window is marked as the five days before ovulation plus ovulation day itself, because sperm can survive for several days while the egg lives for roughly one.
Cycle length is not fixed for most people. Illness, travel, stress, sleep, weight change and a great many ordinary things can shift ovulation by a few days, and the predicted dates shift with it. A calculator can only work from the numbers you give it.
That is why writing down your actual start dates matters more than any single prediction. Two or three months of real dates will tell you far more about your own pattern than an estimate ever can, which is exactly what our free printable tracker is for.
Worth speaking to a doctor about: periods that stop for three months or more without pregnancy, bleeding that soaks through protection every hour for several hours, periods lasting longer than seven days, severe pain that stops you going about your day, or bleeding between periods. None of these mean something is certainly wrong, but all of them are worth a professional opinion rather than a calculator.
