Every cycle is a little different, but most last somewhere between 21 and 35 days, counted from the first day of one period to the first day of the next. Ovulation usually happens roughly two weeks before your next period starts — not necessarily on "day 14," which is a common myth.

If your cycles are fairly regular, our Period Calculator can give you a reasonable estimate of when your next one is due — often the first step before trying to track ovulation more precisely.