Ovulation calculator

The term ‘cycle’ is shorthand for a woman’s menstrual cycle. A woman’s menstrual cycle refers to the hormonal and reproductive system changes that make a pregnancy possible.

A typical menstrual cycle, which begins on the first day of your period until the first day of your next period, lasts anywhere between 28 to 35 days. However, it is normal for cycle lengths to vary between women. For example, some women may have regular cycles that last around 24 days.

The two phases that make up your menstrual cycle are the follicular phase and the luteal phase.

The follicular phase occurs from the first day of your period up until ovulation. During this phase, estrogen levels in your body increase leading to ovulation. The lining of your uterus also begins to thicken to support a possible pregnancy once your period has stopped.

The luteal phase occurs after ovulation until the first day of your period (when the lining of your uterus sheds). It predominantly involves an increase in progesterone which supports the thickening of your uterus lining. If sperm fertilises the egg, the resultant embryo can attach to the wall of the uterus. However, if fertilisation does not occur, progesterone levels decrease and the lining of the uterus sheds.

Day 1 of your LMP is the start date of your last period – i.e. the first day you began menstruating at full flow (ignoring spotting and light bleeding).

Typically, a woman is most fertile 2–4 days before ovulation up until the day of ovulation itself. That’s why if you’re trying to conceive, we recommend timing sexual intercourse to occur on these dates.

If your cycle length is irregular, we recommend seeking help from a fertility specialist. Shorter than normal cycle lengths may indicate poor egg quality, anovulation (the absence of egg release) or a short luteal phase. Other irregular cycle patterns may indicate that you are experiencing unreliable ovulation, or the timing of your ovulation is too hard to pinpoint accurately.

Women with regular cycles

If you are under 35 years of age and having frequent and unprotected timed sexual intercourse, we recommend seeking the opinion of a fertility specialist after 12 months of trying. Your fertility specialist will be able to guide you on whether you and/or your partner would benefit from fertility testing.

If you are over 35, we recommend seeking help if you have been trying for 6 months without success, as fertility declines with age.

You can also see a fertility specialist any time that you are concerned about your ability to conceive.

Women with irregular cycles

If you are under 35 years of age and having frequent and unprotected time sexual intercourse, you should seek assistance from a fertility specialist after 4–6 months of trying. Your fertility specialist will be able to guide you on whether you and/or your partner require a formal fertility assessment to determine why you may be having difficulty conceiving.

As your ovarian reserve (the pool of eggs left in your ovaries with reproductive potential) naturally declines with age, we recommend seeking assistance if you are 35–39 and have been trying for just 3 months. If you are over 40 years of age, we recommend contacting a fertility specialist as soon as possible.