An app that tells you which phase of your cycle you’re in

The four phases, why the middle of the cycle is the hard part, and exactly how Bloom decides which phase you’re in today.

Last reviewed 14 October 2026Checked against the sources listed below

This page is for you if you want to open an app and see, plainly, which phase of your cycle you are in today, and how sure it is about that. It covers how the four phases are usually defined, why the middle of the cycle is the hardest part to pin down, and exactly how Bloom works out your phase from what you log.

The four phases, briefly

Most descriptions split the menstrual cycle into four phases. They follow the hormones: estrogen rises after your period, an egg is released at ovulation, and progesterone rises afterwards until both fall and the next period starts.^[1]

• Menstrual: your period. Cleveland Clinic says most people bleed for three to five days, and that three to seven days is considered normal.^[2]
• Follicular: from the end of your period up to ovulation, as estrogen climbs.
• Ovulation: the short window when an egg is released. In a 28-day cycle it usually falls around day 14, according to Cleveland Clinic.^[2]
• Luteal: from ovulation to your next period. Cleveland Clinic gives an average of 12 to 14 days, and treats 10 to 17 days as normal.^[3]

Why the middle of the cycle is the hard part

Day 14 is a textbook number. Real cycles move around, and most of the movement is in the first half. In an analysis of more than 600,000 cycles logged by users of a fertility app, the follicular phase averaged 16.9 days but ranged from about 10 to 30, while the luteal phase averaged 12.4 days and stayed between about 7 and 17.^[4] So if your cycle is 34 days long, your ovulation is far more likely to be around day 20 than day 14.

That is why a phase tracker that simply cuts every cycle into four equal blocks, or assumes day 14 for everyone, will often tell you the wrong phase. The period itself is easy: you know when you are bleeding. The days between periods are where an app has to estimate, and where it should say so.

How Bloom works out your phase

Bloom shows your current phase and the day of your cycle every time you open it. Here is what sits behind that:

• Your period comes from your log. While you have logged a period that hasn’t ended, Bloom shows the menstrual phase as fact, not as a guess. When you log that it has ended, the follicular phase starts that same day.
• Ovulation is counted back from your next period, not forward from the last one. Bloom assumes a 14-day luteal phase to start with, so a longer cycle gets a longer follicular phase rather than an ovulation day stuck at 14.
• Your own signs can refine it. If you log ovulation tests or cervical fluid, Bloom uses them to place the phases. Once it has seen two cycles where those signs line up, it uses your own luteal length (anything from 9 to 18 days) instead of the default.
• Your cycle length comes from your recent history. Bloom predicts from the median of your last six cycles, so one unusual month doesn’t throw every phase off.
• A late period doesn’t start a new cycle. If your period is due and hasn’t come, Bloom keeps you in the luteal phase and tells you it is waiting, instead of starting a fresh cycle on schedule.
• It says when it is estimating. For your first three cycles, Bloom marks its reading as an estimate and counts down the cycles it still needs. After that it shows the rhythm it has actually seen in your logs.

What you see for each phase

Knowing the name of the phase is only useful if it tells you something. For each phase Bloom gives you guidance on what the phase often brings, a chart of how the hormones typically move, and a place to set one focus for the phase. The hormone charts are educational curves, drawn from typical patterns. They are not your own hormone levels, because nothing in a phone app can measure those.

When you do a check-in, Bloom compares your day with what your phase usually brings. Over a few cycles that shows you whether the textbook description of a phase fits you, or whether your own pattern is different. If you want to plan around your phases, the cycle syncing page covers how that works.

What Bloom can’t tell you

• It can’t confirm that you ovulated. Bloom doesn’t read a thermometer or test strips, and a positive test you log is a sign, not proof. Irregular cycles can happen without ovulation at all.^[5]
• It can’t measure your hormones. Phases after your period are estimates from your dates and the signs you log.
• It is not a fertility tool or contraception. Bloom’s ovulation phase should never be used to plan or avoid a pregnancy.
• It works less well when cycles vary a lot. If your cycle swings by weeks, any app’s mid-cycle phases are rough. The irregular periods page explains how Bloom handles that.

Getting an accurate phase reading

• Log the first day of every period, and the day it ends. Those two dates anchor everything else.
• Give it three cycles. Early phases lean on the cycle length you typed in at the start; your real pattern takes over as you log.
• Add signs if you already track them. If you use ovulation tests, logging the results lets Bloom move your ovulation phase to where your body puts it.
• Trust how you feel over the label. If the app says follicular and you feel flat, that is useful information about you, not a mistake on your part.

Bloom is a wellness and planning app. It is not a medical device, it does not diagnose or treat any condition, and it is not a method of contraception. This page is general information, not medical advice. If something about your cycle worries you, talk to a doctor, nurse or midwife.