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As ovulation (production of a mature egg) is essential for a regular menstrual cycle, women who have a regular cycle in the normal range are usually ovulating regularly. Conversely, women who do not ovulate regularly have irregular and usually infrequent periods.

The time of ovulation depends on the length of the menstrual cycle. If a woman has a 28-day cycle, ovulation occurs at around day 14, and if she has a 21-day cycle, ovulation occurs at around day 7. The time taken to mature an egg and ovulate can vary from woman to woman. The part of the cycle during which the egg develops is called the follicular phase, as the egg develops in a small ‘follicle’ or cyst in the ovary. However, the time from ovulation to a period (if fertilization does not occur) is fixed at around 14 days. This is called the secretary phase of the cycle as the ovary makes and ‘secretes’ progesterone. Provided your cycle is regular, you will be able to estimate when you will be ovulating.