Ovulation itself is surprisingly brief. The physical release of an egg from your ovary takes only a few seconds, and that egg survives just 12 to 24 hours before your body reabsorbs it. But if you’re asking this question because you’re trying to get pregnant or avoid pregnancy, the window that actually matters is wider than that single day.
How Long the Egg Lasts
Once your ovary releases an egg, it travels into the fallopian tube and remains viable for roughly 12 to 24 hours. If sperm doesn’t reach it during that time, the egg breaks down and is reabsorbed by your body. This is the only point in your cycle when fertilization can happen.
The trigger for this release is a sharp rise in luteinizing hormone (LH). About 36 to 40 hours after this hormone spikes, the egg is released. That’s why ovulation predictor kits test for LH in your urine: a positive result means ovulation is likely coming within the next day or two, not that it’s already happened.
Why Your Fertile Window Is Longer Than 24 Hours
Sperm can survive inside the uterus and fallopian tubes for 3 to 5 days. That means sex that happens several days before ovulation can still result in pregnancy, because sperm may already be waiting when the egg arrives. Combined with the egg’s own 12 to 24 hour lifespan, your total fertile window stretches to about 5 to 6 days per cycle: the five days leading up to ovulation plus the day of ovulation itself.
The highest chance of conception comes from the two days before ovulation and the day it occurs. By the day after ovulation, the window has typically closed.
Ovulation Day Varies More Than You Think
Many people assume ovulation always falls on day 14 of a 28-day cycle. In reality, it’s far less predictable. A large prospective study published in Human Reproduction found that 96.5% of women experienced ovulation timing fluctuations of 4 days or more over a 12-month period, and more than half saw their ovulation day shift by a full week or more across 12 cycles. The average fluctuation was about 10.7 days per woman within a single year.
Even more striking: while 50% of ovulations in the study occurred between cycle days 12 and 16, nearly 46% of the cycles that resulted in conception involved ovulation after day 16. If you’re relying on a calendar alone to estimate your fertile window, you’re working with a very rough guess.
Signs That Ovulation Is Approaching
Your body gives several signals that ovulation is near, though none of them pinpoint the exact hour.
Cervical mucus changes are one of the most reliable day-to-day indicators. In the days before ovulation, discharge shifts from thick and white to clear, slippery, and stretchy, often compared to raw egg whites. This texture typically lasts about three to four days and signals your most fertile time. The consistency isn’t random: this type of mucus creates a more hospitable environment for sperm to travel through.
Ovulation pain is a one-sided, lower abdominal ache that some women feel around the time of egg release. It can last anywhere from a few minutes to a day or two. The pain likely comes from the follicle stretching the ovary’s surface before rupture, or from fluid released afterward irritating the abdominal lining. Not everyone experiences it, and those who do don’t necessarily feel it every cycle.
How to Track Your Ovulation Window
Ovulation Predictor Kits
These urine-based tests detect the LH surge that precedes egg release. Accuracy across popular brands ranges from about 92% to 97% when compared against blood LH measurements. A positive result gives you roughly a 24 to 40 hour heads-up that ovulation is coming, making these kits useful for timing intercourse. Price differences between brands don’t translate to meaningful accuracy differences, though sensitivity (how well they catch a genuine surge) does vary, with some budget options actually performing better than pricier ones.
Basal Body Temperature
Your resting temperature rises slightly after ovulation, typically by less than half a degree Fahrenheit (anywhere from 0.4°F to 1°F). The catch is that this shift confirms ovulation has already happened, so it’s more useful for understanding your cycle patterns over several months than for predicting the current month’s fertile window in real time. You’ll need to take your temperature at the same time each morning before getting out of bed to get consistent readings.
Combining Methods
No single tracking method is perfect on its own. Cervical mucus tells you fertility is rising, an ovulation kit tells you the hormonal trigger has fired, and temperature confirms ovulation occurred. Using two or three of these together gives you a much clearer picture of your personal pattern than relying on any one signal. Over a few months, you’ll start to see how your body’s timeline compares to the textbook version, and you can plan accordingly.