What phase of my cycle am I in today?
Enter the first day of your last period. You get your cycle day, your phase, when you are likely to ovulate and bleed next, and how to run and lift today.
Day 1 is the first day of full bleeding, not spotting. Not sure of your length? Leave it at 28.
Your phase today
Enter the first day of your last period
You will see your cycle day, your phase, and how to run and lift today.
An estimate from the calendar, not a test, and not contraception: it can not tell you when you are fertile. If your periods are very painful, very heavy, or regularly more than 35 days apart, see a doctor.
Your menstrual cycle has four phases: menstrual, follicular, ovulatory and luteal. Which one you are in depends on your own cycle length, not a textbook 28 days, because ovulation happens about 14 days before your next period rather than on day 14. This calculator uses the same phase model as the Phaes app, then shows how the app would shape your training for that phase.
How the calculator works
It counts from the first day of your last period (day 1) and places ovulation about 14 days before your next expected period, because the luteal phase is the part of the cycle that varies least between women. The few days around ovulation are the ovulatory phase, the days before it are follicular, and the days after it are luteal. On a 28-day cycle that puts ovulation around day 14. On a 32-day cycle it is closer to day 18, which is why a fixed calendar so often gets it wrong.
It is an estimate. Cycles vary from month to month, and only tracking (a rise in basal temperature, LH tests, or a few months of logged periods) confirms when you actually ovulate. For a day-by-day view, see what each cycle day means: day 1, day 14, day 21, or day 28.
How to train in each phase
Menstrual phase
Estrogen and progesterone are at their lowest. Keep it gentle if you feel rough (an easy run, a walk, a rest day), and train as normal if you feel fine. Phaes eases the top-end strength effort here.
Follicular phase
Estrogen climbs and many women feel their best. It is a good window for quality runs (intervals, hills, sprints) and for building strength volume.
Ovulatory phase
Estrogen peaks and LH surges. Phaes treats it as the peak strength window and pushes the hardest set of the cycle here.
Luteal phase
Progesterone rises, and with it your temperature and resting heart rate, so the same pace feels harder. Lower the intensity ceiling, favour steady aerobic running, hold strength at maintenance, and place a full rest day here. In the last week both hormones fall, which is when premenstrual symptoms show up.
How much does cycle phase really matter?
Less than social media suggests. A 2020 meta-analysis of 78 studies found performance may be trivially lower in the early follicular phase (around your period), with large differences between women and low-quality evidence overall (McNulty et al., Sports Medicine). Its conclusion was to personalise rather than follow a general rule. That is how Phaes uses phase: as one input next to your sleep, energy, soreness and symptoms from a daily check-in, never as the only one.
Perimenopause, menopause and hormonal contraception
If your cycles have become irregular, ovulation may or may not happen and hormones swing rather than follow a pattern, so no calendar can tell you your phase. After menopause there are no phases at all, and most hormonal contraception switches off the natural cycle. In all three cases the calculator says so rather than guessing, and the training answer is the Phaes method for the menopause transition: short sprints over long slow miles, lifting heavy, easy days that are genuinely easy, one full rest day a week, and a reset week every fourth week. Read how Phaes trains with your cycle.
Let the plan follow your real cycle
A calculator gives you one day. Phaes anchors to the periods you actually log, projects your phases from your own cycle, and moves your hard sessions, strength and rest days around them and your daily check-in.
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Questions women ask about this
How do I know what phase of my cycle I am in?
Count from the first day of your last period, which is cycle day 1. Days 1 to about 5 are the menstrual phase. Ovulation happens about 14 days before your next period, so subtract 14 from your usual cycle length to find it: day 14 on a 28-day cycle, day 18 on a 32-day one. The days before ovulation are follicular and the days after it are luteal.
Is ovulation always on day 14?
No. Day 14 is only typical for a 28-day cycle. Ovulation happens roughly 14 days before your next period, so a 24-day cycle ovulates around day 10 and a 35-day cycle around day 21. It can also shift from one month to the next.
Should I train differently in each phase?
It can help as a starting point: harder sessions and strength building in the follicular and ovulatory phases, steadier running and maintenance strength in the luteal phase, and gentler days during your period if you feel rough. The research on phase and performance is weak and individual, so how you feel on the day should win.
Can I use this calculator in perimenopause?
Not to predict phases. When cycles become irregular, hormones fluctuate rather than follow the usual pattern, so the calculator tells you that and gives the training approach that works through the transition instead.
Can this calculator tell me when I am fertile?
No. It is a calendar estimate for training and should never be used as contraception or to plan a pregnancy. Ovulation can move by several days from cycle to cycle.