# The four phases, in depth > Menstrual, follicular, ovulation and luteal, and what each one is doing. Category: Cycle basics · 5 min read · Written by the Splash team · Sources checked October 2026 URL: https://splash.care/learn/cycle-basics/four-phases ## Quick answer The menstrual cycle has four phases: menstrual (your period, about 2 to 7 days), follicular (from day 1 until ovulation, the part that varies most), ovulation (an egg is released, about 12 to 16 days before the next period) and luteal (from ovulation to the next period, roughly 10 to 16 days). - Menstrual and follicular phases overlap: both start on day 1. - Ovulation is triggered by an LH surge and happens roughly 10 to 16 days before your next period. - Progesterone from the corpus luteum runs the luteal phase, which averages about 12 days, not always 14. - Most of the variation in cycle length comes from the follicular phase. Think of your cycle like the tide: it rises and falls in a pattern, but no two tides are identical. Doctors usually split the cycle in two (before and after [ovulation](https://splash.care/learn/glossary/ovulation)). Splash uses four phases because it is easier to picture. Here is what is happening beneath the surface in each. ## What happens in the menstrual phase? [Oestrogen](https://splash.care/learn/glossary/oestrogen) and [progesterone](https://splash.care/learn/glossary/progesterone) are at their lowest. The womb lining comes away, which usually takes **2 to 7 days**. Chemicals called [prostaglandins](https://splash.care/learn/glossary/prostaglandins) help the womb contract, which is where [cramps](https://splash.care/learn/period-care/cramp-relief) come from. Behind the scenes, [FSH](https://splash.care/learn/glossary/fsh) is already starting to rise to kick off the next cycle. ## What happens in the follicular phase? Technically this phase starts on day 1 and overlaps with your period, which is why the first two phases share days. FSH prompts several [Follicle](https://splash.care/learn/glossary#follicle)s to grow, and usually one becomes the lead follicle. It makes [oestrogen](https://splash.care/learn/cycle-basics/hormones-explained), which rebuilds the womb lining and makes [cervical mucus](https://splash.care/learn/glossary/cervical-mucus) wetter and stretchier. The [Follicular phase](https://splash.care/learn/glossary/follicular-phase) varies the most in length. In the large app study, it averaged 16.9 days but ranged from about 10 to 30. ## What happens at ovulation? When oestrogen gets high enough, the brain releases a big burst of [LH](https://splash.care/learn/glossary/lh). [Ovulation](https://splash.care/learn/phases/ovulation) follows within about 36 hours. The egg lives for roughly 12 to 24 hours. Sperm can survive for several days, which is why the [fertile window](https://splash.care/learn/glossary/fertile-window) starts before ovulation. The NHS says ovulation happens roughly 10 to 16 days before your [next period](https://splash.care/tools/period-calculator). ## What happens in the luteal phase? The empty follicle turns into the [Corpus luteum](https://splash.care/learn/glossary/corpus-luteum), which makes progesterone. Progesterone makes the lining spongy and supportive and raises your resting temperature by a small amount (about 0.3 to 0.6°C). The [Luteal phase](https://splash.care/learn/glossary/luteal-phase) is steadier than the [follicular phase](https://splash.care/learn/phases/follicular), but it is not a fixed 14 days. The app study found an average of 12.4 days (range about 7 to 17). If no pregnancy happens, the corpus luteum fades, hormones drop, and your next period starts. - **Period:** Hormones low, lining sheds. Rest and warmth are your friends. - **Follicular:** Oestrogen climbs. Many people notice energy and mood lifting. - **Ovulation:** LH surges, an egg is released. Discharge often turns clear and stretchy. - **Luteal:** Progesterone leads. Some people feel PMS symptoms in the final days. **Myth:** Ovulation always happens 14 days after your period starts. **Fact:** That is only true for a 28-day cycle that runs perfectly. The NHS puts ovulation at about 10 to 16 days before your next period, so a 35-day cycle usually ovulates around day 19 to 25, not day 14. **Myth:** The luteal phase is always exactly 14 days. **Fact:** It is steadier than the follicular phase, but real-world data show it varies by several days between people (about 7 to 17 days in a study of over 600,000 cycles). > **Splash says:** phases in Splash are estimates based on your logs, not measurements. Adding LH tests or temperature gives the ovulation guess real evidence behind it. **Quick quiz:** Which phase varies most in length between cycles? 1. Follicular 2. Luteal 3. They are always equal Answer: Follicular. The follicular phase stretches or shrinks. The luteal phase is steadier, though it is not an exact 14 days. **Quick quiz:** What triggers ovulation? 1. A surge of LH 2. Your period ending 3. A rise in progesterone Answer: A surge of LH. Rising oestrogen triggers a burst of LH from the brain, and the egg is released within about 36 hours. Progesterone rises after ovulation. ## Questions people ask ### Which phase of the cycle am I in? Count from the first day of your last period. Days 1 to about 5 are usually the menstrual phase; the follicular phase runs until ovulation; ovulation is usually 12 to 16 days before your next period; the luteal phase follows. A free cycle phase calculator can estimate it for you. ### Which phase is the longest? The follicular phase usually is, and it is also the one that varies most. The luteal phase is more consistent, typically around 10 to 16 days. ## Sources 1. [NHS: Periods and fertility in the menstrual cycle](https://www.nhs.uk/conditions/periods/fertility-in-the-menstrual-cycle/) 2. [Cleveland Clinic: Menstrual cycle](https://my.clevelandclinic.org/health/articles/10132-menstrual-cycle) 3. [Cleveland Clinic: Ovulation](https://my.clevelandclinic.org/health/articles/23439-ovulation) 4. [Bull et al. (2019) Real-world menstrual cycle characteristics of more than 600,000 menstrual cycles, npj Digital Medicine](https://pmc.ncbi.nlm.nih.gov/articles/PMC6710244/) This is general information, not medical advice. Splash can’t diagnose. If you’re worried, talk to a GP, pharmacist or sexual health clinic. In an emergency call 999 (UK) or 911 (US).