Ovulation Phase: Signs, Timing and What to Know

Ovulation is when an ovary releases a mature egg, and it is the phase of your cycle when pregnancy is most likely. In a 28-day cycle it usually happens around day 14, but the exact day varies from person to person and from cycle to cycle. The egg lives for only about 12 to 24 hours, though the fertile window is longer.

Quick summary: Ovulation is triggered by a surge of LH. It tends to happen about 12 to 16 days before your next period, not always on day 14. Signs include clear, slippery mucus and sometimes mild one-sided cramping, but many people notice nothing. Tracking ovulation is not birth control.

What happens during ovulation

During the follicular phase, follicles in your ovaries grow and one becomes dominant. As that follicle matures, it produces more estrogen. When estrogen is high enough, it triggers a surge of luteinizing hormone (LH). The LH surge prompts the ovary to release the mature egg, which then starts moving toward the fallopian tube.

The Office on Women's Health says LH rises about 36 hours before ovulation and peaks about 12 hours before. The release itself only takes seconds, according to Cleveland Clinic.

After ovulation, the empty follicle becomes the corpus luteum and the luteal phase begins. For more on the hormones, see estrogen, progesterone, LH and FSH across your cycle.

When do you ovulate?

The common answer is "day 14," but that applies to a 28-day cycle. A better way to think about it is counting backward from your next period. The NHS says ovulation happens about 12 to 16 days before your next period starts. The Office on Women's Health notes that the time from ovulation to your next period can range from 7 to 19 days.

That means:

• If your cycles are shorter, you may ovulate earlier.
• If your cycles are longer, you may ovulate later.
• If your cycles vary, your ovulation day will probably move around too.

Cycle lengths of about 21 to 35 days are considered normal by both the NHS and Cleveland Clinic. See how long a normal menstrual cycle is.

Signs of ovulation

Not everyone notices signs, and they can begin days before ovulation. According to Cleveland Clinic, common ones include:

• Breast tenderness
• Bloating
• Mild pelvic or abdominal cramping on one side (sometimes called mittelschmerz)
• Light spotting
• Increased sex drive
• Mood or appetite changes

The Office on Women's Health also lists:

• More slippery, clear vaginal mucus a few days before ovulation
• A slight rise in basal body temperature after ovulation

These are tendencies. Having no signs does not mean something is wrong.

How people track ovulation

Cleveland Clinic lists several methods:

• Cycle tracking: Logging period start dates and symptoms over several months, using an app or calendar.
• Cervical mucus: Noticing when it turns clear and slippery.
• Ovulation predictor kits: These detect the LH surge in urine. A positive result usually means ovulation within about 36 hours.
• Basal body temperature: Temperature rises roughly 0.5 to 1 degree after ovulation. You take it each morning before getting up, and look at the pattern over months. Because the rise happens after ovulation, it confirms ovulation looking back rather than predicting it.

More on getting started is in how to track your period and cycle.

The fertile window

The egg survives about 12 to 24 hours after release. Sperm can live for several days, so the fertile window begins before ovulation. Cleveland Clinic says pregnancy is possible from about 5 days before ovulation through about 1 day after. The NHS notes that sperm can survive for up to 7 days.

Important: tracking ovulation is not contraception

Estimating your ovulation day or fertile window is not birth control. Ovulation can shift because of stress, illness, travel or just natural variation, and apps and calendars can only estimate.

The NHS describes fertility awareness methods as 91 to 99 percent effective only when followed perfectly and consistently, dropping to about 76 percent with imperfect use. They also do not protect against STIs. The NHS adds that it can take 2 to 3 cycles to learn the method, and that you should use other contraception while learning.

If you want to prevent pregnancy, talk to a doctor, nurse or sexual health clinic about methods that suit you.

Ovulation and trying to conceive

If you are trying to get pregnant, tracking can help you spot your fertile days. The NHS suggests that having sex every 2 or 3 days is a way to cover your fertile window. If you have irregular periods and are trying to get pregnant, the NHS advises speaking to a doctor.

When to talk to a doctor

See a doctor if:

• You have very irregular cycles or go 3 months or more without a period (see irregular periods)
• You have severe pelvic pain, especially if it is new or one-sided and intense
• You are trying to conceive and have concerns about ovulation
• Your symptoms are affecting your daily life

Where Mochi Moon fits

Mochi Moon, an iPhone app launching in fall 2026, shows predictions for your next period and an estimated fertile window, plus a phase guide for the ovulation phase. These are estimates only and are not birth control.