How long is each phase of the menstrual cycle?
In a typical cycle, the menstrual phase (your period) lasts 2 to 7 days, the follicular phase (day 1 to ovulation) averages about 16 to 17 days but ranges from 10 to 30, ovulation is a single day within a fertile window of about 6 days, and the luteal phase lasts 12 to 14 days. When cycle length changes, it's usually the follicular phase that changed.
Phase lengths at a glance
| Phase | Typical length | Normal range | Varies a lot? |
|---|---|---|---|
| Menstrual (your period) | About 5 days | 2 to 7 days | Somewhat |
| Follicular (day 1 to ovulation, includes your period) | About 16 to 17 days | About 10 to 30 days | Yes: the main source of variation |
| Ovulation | The egg lives 12 to 24 hours | Fertile window about 6 days | Timing shifts with the follicular phase |
| Luteal (after ovulation to the next period) | About 12 to 14 days | About 7 to 17 days | Much less |
These numbers come largely from a study of over 600,000 cycles tracked in an app, which found an average cycle of 29.3 days, an average follicular phase of 16.9 days and an average luteal phase of 12.4 days. Only a minority of cycles were exactly 28 days. See the full overview of the phases of the menstrual cycle.
Why the follicular phase varies most
The follicular phase ends when you ovulate, and ovulation only happens once a follicle has grown and estrogen has been high long enough to trigger the LH surge. That process is sensitive. Stress, illness, travel, sleep changes, intense training, under-eating, breastfeeding, PCOS and coming off hormonal contraception can all slow it down. So a cycle that runs late almost always means ovulation came late, not that the luteal phase got longer.
Why the luteal phase is steadier
The luteal phase is controlled by the lifespan of the corpus luteum, which usually lasts about two weeks unless pregnancy keeps it going. That's why NHS guidance says ovulation happens about 12 to 16 days before your next period, and why counting back from your expected period is a better way to estimate ovulation than counting forward from day 1. Try our luteal phase calculator.
Phase lengths for different cycle lengths
| Cycle length | Period | Follicular phase | Ovulation (approx.) | Luteal phase |
|---|---|---|---|---|
| 24 days | Days 1 to 4 | About 10 days | Around day 10 | About 14 days |
| 28 days | Days 1 to 5 | About 14 days | Around day 14 | About 14 days |
| 32 days | Days 1 to 5 | About 18 days | Around day 18 | About 14 days |
| 35 days | Days 1 to 5 | About 21 days | Around day 21 | About 14 days |
These are estimates using a 14-day luteal phase. Your own luteal phase might be 11 or 13 days, which shifts ovulation by a day or two. Our what phase am I in tool does the math for your cycle.
How phase lengths change with age
- Teens: cycles are often longer and irregular for the first few years, as ovulation isn't always regular yet.
- 20s to 40s: in the large app study, cycle length and follicular phase length both shortened by about 0.2 days for every year of age from 25 to 45.
- Perimenopause: the follicular phase often shortens first, then cycles become irregular, with skipped ovulations and longer gaps.
Why phase length matters for mood
If your harder days usually come in the last week of the luteal phase, knowing your real phase lengths tells you when they're coming. Because the luteal phase is fairly steady, your PMS days are often more predictable than your ovulation day. A long follicular phase simply means a longer stretch of lighter days before the luteal dip. See luteal phase mood.
Lulu learns your real cycle and phase lengths from your logged periods, and can use Apple Watch wrist temperature via Apple Health to refine ovulation estimates. Your mood check-ins show how each phase usually feels.
See a doctor if your cycles are often shorter than 21 or longer than 35 days, if your cycle length varies by more than 7 to 9 days from month to month, if your luteal phase is regularly under 10 days and you're trying to conceive, if your period lasts more than 7 days, or if your periods stop for 3 months or more.
Frequently asked questions
Which phase of the menstrual cycle is the longest?
Usually the follicular phase, which includes your period and averages about 16 to 17 days. It also varies the most.
How long is the luteal phase?
Usually 12 to 14 days, with about 10 to 17 days considered common. It's the steadiest phase.
How many days does ovulation last?
The egg lives 12 to 24 hours after release. The fertile window, including the days sperm can survive beforehand, is about 6 days.
Why is my cycle longer this month?
Most likely ovulation came later than usual, lengthening the follicular phase. Stress, illness and travel are common reasons. If you could be pregnant, take a test.
Is a 10-day luteal phase normal?
It's at the short end of normal. A luteal phase under 10 days is sometimes called short and is worth discussing with a doctor if you're trying to conceive.
Sources
- Bull JR et al. Real-world menstrual cycle characteristics of more than 600,000 menstrual cycles. npj Digital Medicine (2019)
- NHS: Periods
- Cleveland Clinic: Luteal Phase of the Menstrual Cycle
- Cleveland Clinic: Follicular Phase of Menstrual Cycle
This page is for information only and isn鈥檛 medical advice. If something worries you, please talk to a doctor.
Keep reading
The 4 phases of the menstrual cycle, in colorThe 4 phases of the menstrual cycle explained simply: what your hormones do in each, how long each lasts, and how mood and energy usually change.
How long is the luteal phase?How long is the luteal phase? Usually 12 to 14 days, with 10 to 17 considered normal. How to measure yours, what a short one means, and why it matters.How long is the follicular phase?How long is the follicular phase? About 17 days on average, but anywhere from 10 to 30 days is common. Why it varies and how it sets your cycle length.
Luteal phase calculator: how long is my luteal phase?Free luteal phase calculator: enter your ovulation day and next period to see your luteal phase length and whether it sits in the typical 11 to 17 day range.
Cycle length calculator: is my cycle normal?Free cycle length calculator: enter the start dates of your last few periods to get your average cycle length and see whether your cycle counts as regular.How long is a normal menstrual cycle?How long is a normal menstrual cycle? Anywhere from 21 to 35 days in adults. What's average, how much variation is fine, and when to see a doctor.