Three-cycle period and ovulation forecast
Predictions assume a consistent cycle. Record several cycle start dates and use their average for a more representative estimate.
Next three cycles
Evidence-based guide
Period prediction uses the interval from the first day of one period to the first day of the next. Averaging several recent cycles can provide a useful planning estimate, but future dates remain forecasts because cycle length naturally varies.
Count from day one of bleeding through the day before the next period begins.
Describes the expected number of bleeding days and does not change the projected start of the following cycle.
The visual forecast places ovulation roughly 14 days before the next predicted period and marks the preceding fertile window.
The three-cycle display is best used for scheduling and pattern awareness. Predictions become less certain farther into the future. Update the calculator whenever an actual period begins so later forecasts reflect the newest information.
This tool does not diagnose pregnancy, hormonal conditions, or abnormal bleeding. Hormonal contraception, postpartum changes, perimenopause, illness, and stress can make historical averages unreliable.
Day one is the first day of menstrual bleeding, rather than light spotting that occurs beforehand.
Consistency matters more than matching 28 days; cycles that vary substantially are harder to predict with a calendar.
Ovulation timing can shift with stress, illness, travel, sleep changes, nutrition, and normal biological variation.
Contact a clinician for very heavy bleeding, severe pain, bleeding between periods, possible pregnancy, or persistent major cycle changes.
