Predict your upcoming menstrual period dates, along with your ovulation and fertile window for each cycle over the next several months.
A menstrual cycle begins on the first day of your period and ends the day before your next period starts. The calculator predicts future periods by adding your average cycle length (typically 21–35 days) repeatedly to your last period date.
Most cycles range from 21 to 35 days, with an average of 28 days. Period duration typically lasts 2–7 days. Cycle length can vary month to month due to stress, illness, diet, exercise, and hormonal changes.
Note: This calculator assumes a regular cycle. If your cycle is irregular, predictions may be less accurate. Consult a healthcare provider for irregular cycles.