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Menstrual Cycle Phase Calculator
Enter the first day of your last period and your usual cycle length to find out which phase you are in today: menstrual, follicular, ovulatory or luteal. You also get the date each phase starts, a color-coded 3-month calendar and a table of the next three cycles.
Last updated:
Day 1 is the first day of full bleeding.
Leave as today, or pick any later date.
days
From one period's first day to the next. 21–35 is common.
days
days
Leave at 14 unless you track ovulation.
Enter your values to see the result.
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How to use the Menstrual Cycle Phase Calculator
- Enter the first day of your last period (day 1 is the first day of full flow).
- Set your average cycle length and how many days your period usually lasts.
- Keep the luteal phase at 14 days unless you track ovulation and know yours.
- Read your current phase, cycle day and the next phase change.
- Check the calendar and table to plan ahead, or pick another date to check.
Cycle phases at a glance
| Phase | 28-day cycle | Main hormones | What many people notice |
|---|---|---|---|
| Menstrual | Days 1–5 | Estrogen and progesterone low | Bleeding, cramps, lower energy |
| Follicular | Days 6–12 | FSH, then rising estrogen | Energy and mood often lift |
| Ovulatory | Days 13–15 | Estrogen peak, LH surge | Clear, stretchy cervical mucus; most fertile days |
| Luteal | Days 16–28 | Progesterone high, then falls | Possible PMS late in the phase: bloating, tender breasts, mood changes |
Strictly speaking, the follicular phase starts on day 1 and overlaps the period. This calculator uses the popular four-phase view so each day has one label.
How the phases are calculated
- Cycle day = (days since the first day of your last period mod cycle length) + 1. Future dates are projected by repeating your average cycle.
- Ovulation day = cycle length − luteal phase length. For a 32-day cycle with a 14-day luteal phase that is day 18.
- Menstrual: day 1 to your period length. Follicular: the next day until 2 days before ovulation. Ovulatory: the day before to the day after ovulation. Luteal: from 2 days after ovulation to the end of the cycle.
- The fertile window shown is the 5 days before ovulation plus ovulation day, because sperm can survive up to about 5 days.
Tips for better estimates
- Log several period start dates and use your average cycle length; the period calculator can work it out.
- Ovulation tests (LH strips), basal body temperature or cervical mucus changes reveal your real ovulation day and luteal length.
- Stress, illness, travel, intense training, breastfeeding and stopping hormonal birth control can all shift a cycle.
- See a doctor about very painful, very heavy or very irregular periods.
Frequently asked questions
What are the four phases of the menstrual cycle?
The menstrual phase is your period. The follicular phase follows as estrogen rises and an egg matures. The ovulatory phase is the short window around the release of the egg. The luteal phase runs from just after ovulation until the next period, when progesterone is higher.
How does the calculator know which phase I'm in?
It counts the days since the first day of your last period to find your cycle day. Ovulation is estimated at cycle length minus the luteal phase (14 days by default), so day 14 in a 28-day cycle. Days are then split into menstrual, follicular, ovulatory (the day before to the day after ovulation) and luteal.
How long is each phase?
In a typical 28-day cycle the period lasts about 3 to 7 days, the follicular phase runs until ovulation around day 14, the ovulatory window is a few days, and the luteal phase lasts about 12 to 14 days. Differences in cycle length mostly come from the follicular phase.
Why is the luteal phase set to 14 days?
The luteal phase is fairly consistent for most people, commonly 12 to 14 days, while the follicular phase varies more. If you track ovulation with tests or basal body temperature and know your luteal length, enter it for a more personal estimate.
Can I use this to avoid pregnancy?
No. It estimates phases from averages, and ovulation can come earlier or later than predicted. It is not a method of birth control.
My cycle is irregular. Will this work?
It will give a rough guide based on the average length you enter, but phase dates will be less accurate when cycle lengths vary a lot. Update the first day of each new period to keep the prediction current, and talk to a doctor if your cycles are often outside 21 to 45 days.
Are all the tools on FreeToolCabin tested for quality and accuracy?
Yes! Every tool on our site undergoes automated Q/A testing in real browser environments to ensure high precision, correct output, and zero errors. If you happen to spot a bug or have a suggestion, please contact us at [email protected] and our team will review it right away.
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