Track your menstrual cycle, predict your next period and calculate fertile window. Based on your cycle length.
This period and cycle calculator estimates your next periods and fertile window based on the first day of your last period, your average cycle length and your period length. It's a simple way to track your cycle, plan ahead and understand your body's rhythm.
This tool provides general information only and is not medical advice or a contraceptive method. Cycles naturally vary, so predictions are estimates. If your cycle is very irregular or you have concerns, speak with your GP or a women's health professional.
Tracking your cycle helps you plan ahead — knowing roughly when your next period is due makes it easier to prepare for travel, events, sport and appointments. This calculator projects your next few periods and estimated fertile window from three inputs: the first day of your last period, your average cycle length and how long your period usually lasts.
Every projection is an estimate. Real cycles commonly range from about 21 to 35 days and can shift with stress, illness, travel, exercise and age, so treat the dates as a guide rather than a guarantee. Tracking a few cycles and updating your average makes the predictions steadily more accurate.
Two important notes: this tool is not a contraceptive method — cycle-based estimates are not reliable for preventing pregnancy — and it is not medical advice. If your cycles are very irregular, unusually painful or have changed noticeably, that is worth discussing with a GP.