A full menstrual cycle lasts 21 to 35 days, with 28 days as a common average. That total is split across four distinct phases, each with its own hormonal profile and duration. The phase that varies most from person to person, and even cycle to cycle, is the follicular phase, which is why no two cycles feel exactly the same.
Menstrual Phase: 2 to 7 Days
The cycle begins on the first day of your period. Bleeding typically lasts 2 to 7 days, with most people experiencing their heaviest flow in the first two or three days before it tapers off. During this phase, the thickened uterine lining from the previous cycle sheds because no pregnancy occurred. Hormone levels, particularly estrogen and progesterone, are at their lowest point, which is why fatigue and low energy are common during menstruation.
The length of your period is one of the more stable parts of your cycle. If it consistently falls within that 2 to 7 day window, it’s considered normal even if it doesn’t match someone else’s pattern exactly.
Follicular Phase: 11 to 27 Days
The follicular phase overlaps with your period and extends beyond it. It starts on the first day of bleeding and ends when you ovulate. In a textbook 28-day cycle, this phase lasts about 14 days, but it can range from roughly 11 to 27 days. This wide range is the single biggest reason cycle lengths differ between people.
Here’s what’s happening inside your body: a hormone called FSH signals your ovaries to start developing several fluid-filled sacs called follicles, each containing an immature egg. Over the course of days, one follicle becomes dominant and starts releasing rising amounts of estrogen. That estrogen surge does two things. It thickens your uterine lining in preparation for a potential pregnancy, and it eventually triggers the brain to release a burst of another hormone, LH, which kicks off ovulation.
Because the follicular phase is so variable, a “late” period usually means ovulation happened later than usual, not that something went wrong after ovulation. Stress, illness, travel, and weight changes can all delay the follicular phase, pushing your entire cycle longer.
Ovulation: About 24 Hours
Ovulation is the shortest phase, lasting roughly 16 to 24 hours. It’s the moment the dominant follicle releases a mature egg into the fallopian tube. Once released, the egg survives for less than 24 hours. The highest chance of conception occurs when sperm meets the egg within 4 to 6 hours of ovulation.
In a 28-day cycle, ovulation typically happens around day 14, but if your cycle is shorter or longer, ovulation shifts accordingly. The fertile window is wider than ovulation itself because sperm can survive in the reproductive tract for up to five days. So the practical window for conception spans about six days: the five days before ovulation plus the day of ovulation.
How to Spot Ovulation
Your body gives a reliable physical signal as ovulation approaches. Cervical mucus changes in a predictable pattern throughout the cycle. After your period, discharge tends to be dry or pasty. As ovulation nears, it becomes creamy and wet, then shifts to a stretchy, slippery texture that resembles raw egg whites. That egg-white consistency marks your most fertile days. After ovulation, discharge dries up again and stays that way until your next period.
On a 28-day cycle, this stretchy, wet mucus typically appears around days 10 to 14. Tracking these changes over a few cycles can help you identify your personal ovulation timing, which is especially useful if your cycles aren’t a perfect 28 days.
Luteal Phase: 10 to 17 Days
After ovulation, the luteal phase takes over and lasts until your next period begins. The average length is 12 to 14 days, with a normal range of 10 to 17 days. Unlike the follicular phase, the luteal phase is relatively consistent from cycle to cycle for the same person.
Once the egg leaves the follicle, the empty follicle transforms into a structure that pumps out progesterone. This hormone maintains and further thickens the uterine lining, creating an environment where a fertilized egg could implant. If no pregnancy occurs, progesterone production drops off sharply around 10 to 12 days after ovulation. That hormone withdrawal triggers the uterine lining to break down, and your period starts, resetting the cycle.
A luteal phase shorter than 10 days can make it difficult to get pregnant. In a short luteal phase, the uterine lining doesn’t have enough time to thicken sufficiently to support an embryo. If you’re tracking your cycle and consistently notice only a week or so between ovulation signs and your period, that’s worth bringing up with a healthcare provider.
Why Your Cycle Length Changes
When your total cycle is shorter or longer than 28 days, the follicular phase is almost always the reason. Someone with a 24-day cycle likely has a shorter follicular phase (around 10 days) while their luteal phase stays the usual 14 days. Someone with a 35-day cycle probably has a follicular phase stretching to 21 days.
Cycles also change with age. In the first few years after periods begin, cycles tend to be longer and less predictable because the hormonal feedback loop is still maturing. During the reproductive years (roughly late teens through early 40s), cycles generally settle into a more regular pattern. As you approach perimenopause, the follicular phase often shortens, which can make cycles noticeably shorter before they eventually become irregular and space out.
Cycle-to-cycle variation of up to 7 or 8 days is common and not a sign of a problem. What matters more than hitting a specific number is whether your cycle falls within the 21 to 35 day range and follows a roughly predictable pattern for you.