The four phases of your cycle
A menstrual cycle runs from the first day of one period to the day before the next. Hormones change through it in a predictable sequence, and it is usually described in four phases. This calculator shows the dates of each phase for your current cycle.
| Phase | Typical days (28-day cycle) | What happens |
|---|---|---|
| Menstrual | Days 1–5 | The uterine lining sheds. Hormone levels are low. |
| Follicular | Days 1–13 | Follicles in the ovary grow and oestrogen rises, thickening the lining. |
| Ovulation | About day 14 | An LH surge releases an egg, which lives for about a day. |
| Luteal | Days 15–28 | Progesterone rises to prepare for a pregnancy; if none, the period follows. |
The menstrual phase overlaps the start of the follicular phase — they are counted from the same day 1.
How cycle length changes the phases
When cycles are longer or shorter, it is mainly the follicular phase that changes. The luteal phase stays close to 14 days. In a 35-day cycle, for example, ovulation is around day 21; in a 24-day cycle, around day 10. That is why the calculator places ovulation by counting back from your next period.
How you might feel in each phase
- Menstrual: cramps, tiredness and lower energy are common.
- Follicular: many people notice rising energy and mood as oestrogen increases.
- Ovulation: clear, stretchy cervical mucus; some feel a one-sided twinge.
- Luteal: breast tenderness, bloating or mood changes (premenstrual symptoms) can appear in the second half.
Everyone is different, and symptoms that disrupt daily life are worth discussing with a doctor.
Using your cycle map
Knowing your phases helps with planning, recognising patterns and, if you are trying to conceive, timing sex for the fertile window. For your fertile window in the next three cycles, use the Ovulation Calculator; for upcoming period dates, the Period Calculator.