Your cycle runs from the first day of one period to the first day of the next. It has four period phases, driven by changing hormones. The days below describe a typical 28-day cycle, so yours may differ.
| Phase | Typical days | What’s happening |
|---|---|---|
| Menstrual | Day 1 to about 5 | Oestrogen and progesterone are low, and the womb lining sheds |
| Follicular | Day 1 to ovulation | Oestrogen rises, a follicle matures, and the lining thickens |
| Ovulation | About day 14 | A surge of LH makes an ovary release an egg |
| Luteal | About day 15 to 28 | Progesterone rises, then falls if there’s no pregnancy |
1. Menstrual phase
This phase starts on the first day of bleeding. A period usually lasts about 5 days, and it can range from 2 to 7 days. Bleeding is usually heaviest in the first 2 days.
2. Follicular phase
This overlaps with your period and lasts until ovulation. It’s the part of the cycle that varies most, which is why cycle lengths differ.
3. Ovulation
Ovulation usually happens 10 to 16 days before your next period. It’s only around day 14 in a regular 28-day cycle, and later in a longer cycle. Around now, discharge often becomes thin, clear and stretchy, like raw egg white. The ovulation calculator estimates your date.
4. Luteal phase
Progesterone prepares the womb lining for a possible pregnancy. If there’s no pregnancy, hormone levels fall and the lining sheds, starting your next period. PMS symptoms happen in this phase. Read more about period symptoms.
How to work out your own cycle length
Say your period started on 3 May and your next period started on 1 June. Your cycle started on 3 May and ended on 31 May, the day before your next period, so it lasted 29 days. Do this for a few cycles to see your typical length and how much it varies.
In that 29-day cycle, you’d expect ovulation 10 to 16 days before 1 June, which is between about 16 and 22 May. This is why the follicular phase, the part before ovulation, is what usually changes when your cycle runs long.
How the phases connect to how you feel
- During your period, cramps are common. Read what helps with period cramps.
- Around ovulation, discharge often changes. Read about discharge before a period.
- In the luteal phase, PMS symptoms can appear, including bloating, sore breasts and mood changes.
If your period doesn’t start when you expected, a later ovulation is one possible reason. The late period checker can help you look at other possible causes.
When your cycle starts
Periods usually start at around age 12, although starting earlier or later is common. Most people have regular periods by 16 to 18. If your periods haven’t started by age 15, see a GP.
What’s normal, and what’s worth checking
Cycles are often longer or less regular in the first few years after your first period. Speak to a doctor if:
- Your cycles are regularly under 21 or over 35 days
- You’ve had no period for 90 days or more, or missed three in a row
- You bleed for more than 7 days, or between periods
- Your periods are very heavy or severely painful
Log your dates in the period tracker to see your own pattern, month after month.