Ovulation itself is extremely brief. The actual release of an egg from the ovary takes only a few seconds. But the window surrounding ovulation where pregnancy is possible lasts about six days, which is what most people really want to know when they search this question.
The reason those two numbers are so different comes down to how long sperm and eggs each survive inside the body, and understanding that distinction can help whether you’re trying to conceive or trying to avoid it.
How Long the Egg Survives
Once the egg leaves the ovary, it stays viable for just 12 to 24 hours. If sperm doesn’t reach and fertilize it within that narrow window, the egg breaks down and is reabsorbed by the body. This is why ovulation day itself is short in terms of the egg’s actual lifespan, and why timing matters so much for conception.
The Six-Day Fertile Window
Sperm can survive inside the reproductive tract for up to five days. That means sex up to five days before ovulation, or one day after, can result in pregnancy. Combined with the egg’s 12-to-24-hour survival, this creates a fertile window of roughly six days per cycle. The most likely days for conception are the two to three days leading up to ovulation and ovulation day itself, since sperm that’s already waiting in the fallopian tubes has the best chance of meeting the egg.
What Triggers Ovulation
Ovulation is set in motion by a surge of luteinizing hormone (LH), the same hormone detected by at-home ovulation predictor kits. This LH surge begins about 36 hours before ovulation and lasts roughly 24 hours. The egg is typically released between 8 and 20 hours after the LH level peaks. That’s why a positive ovulation test doesn’t mean you’re ovulating right that moment. It means ovulation is likely coming within the next day or so.
When Ovulation Happens in Your Cycle
In a textbook 28-day cycle, ovulation falls around day 14. But cycles vary, and ovulation doesn’t always land on the same day each month. The first half of the cycle (the follicular phase, before ovulation) is the part that fluctuates most. Some months the follicular phase might be 12 days, other months 16 or more. The second half (the luteal phase, after ovulation) is more consistent, typically lasting 12 to 14 days, with anything from 10 to 17 days considered normal.
This means that if your cycle is 30 days one month and 26 the next, ovulation likely shifted earlier or later. You can’t reliably predict ovulation just by counting forward from your period. Counting backward from your expected next period is slightly more accurate, since the luteal phase length stays more stable.
How Ovulation Changes With Age
Ovulation patterns shift over a lifetime. Teenage girls often have irregular ovulation for the first couple of years after their periods start, but most establish a regular pattern by age 16. Cycles then tend to stay predictable, ranging from 26 to 35 days, through the 20s and early 30s.
In the late 30s to early 40s, cycles often start getting shorter, dropping to 21 to 25 days. This happens because the ovaries need more hormonal stimulation to mature an egg, and the process speeds up in response. Eventually, ovulation starts getting skipped altogether, leading to longer, irregular cycles and missed periods as the body transitions toward menopause.
Signs That Ovulation Is Happening
Your body gives several physical clues that ovulation is approaching. The most reliable one you can track at home is cervical mucus. In a typical 28-day cycle, mucus follows a predictable progression: dry or sticky right after your period, then creamy and white, then wet and watery, and finally stretchy and slippery, resembling raw egg whites. That egg-white consistency shows up for about three to four days (roughly days 10 through 14 in a 28-day cycle) and signals your most fertile days. After ovulation, mucus dries up again and stays that way until your next period.
Some people also notice a mild twinge or cramp on one side of the lower abdomen during ovulation, sometimes called mittelschmerz. A slight increase in basal body temperature (your resting temperature first thing in the morning) also occurs after ovulation, though the rise is small, usually only about half a degree, and only confirms ovulation after the fact rather than predicting it in advance.
Tracking Ovulation Accurately
Because ovulation timing shifts from cycle to cycle, relying on calendar math alone isn’t very precise. Combining methods gives you a clearer picture. LH test strips detect the hormone surge 24 to 36 hours before ovulation. Cervical mucus changes give you a broader heads-up, starting three to four days before ovulation. Basal body temperature tracking confirms that ovulation already happened, which is useful for learning your personal pattern over several months.
If you’re trying to conceive, having sex during the days when you notice egg-white cervical mucus or get a positive LH test gives you the best overlap with the fertile window. If you’re trying to avoid pregnancy, keep in mind that sperm’s five-day survival means the fertile window opens well before any of these signs appear.