Menstrual cycle calculator
Menstrual cycle phase calculator
See when each phase of your cycle starts and ends, your fertile window, and which phase you're in today.
Updated
In short
What are the phases of the menstrual cycle?
A cycle has four phases. The menstrual phase is your period. The follicular phase runs from day one until ovulation, while an egg matures. Ovulation is when the egg is released, about 14 days before your next period. The luteal phase runs from ovulation to your next period. You're most fertile in the six days ending on ovulation.
Your cycle phases
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This is an estimate, not a diagnosis or birth control.
General information, not medical advice. Your doctor or midwife can tell you what your own results mean.
How it's calculated
- Ovulation ≈ first day of last period + cycle length − luteal phase (14 days unless you know yours).
- Menstrual phase = the days of your period. Follicular phase = day 1 until the day before ovulation.
- Fertile window = 5 days before ovulation through 1 day after.
- Luteal phase = the day after ovulation until the day before your next period.
Gyne learns your real cycle and adjusts these estimates as you log.
Frequently asked questions
Which phase of the cycle is the longest?
Usually the follicular phase, and it's the one that changes most. The luteal phase stays close to 12 to 14 days for most people, so a longer cycle usually means a longer follicular phase.
How do I know my luteal phase length?
Count the days from ovulation, confirmed with ovulation tests or a temperature rise, to the day before your next period. Gyne can learn it from what you log.
Can I use this to avoid pregnancy?
No. A calendar estimate is not birth control. Talk to your doctor about contraception that works for you.
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