A cycle of 28 days: the menstrual period starts in the first week and ovulation happens around day 14. The woman is fertile 5 days before and 1 day after ovulation.

Cycle

Number of days between the first day of a woman's menstrual period and the first day of the next period. A cycle is about 28 days, but can be a few days longer or shorter. Ovulation takes place about 14 days before the start of the next cycle.