Track your menstrual cycle phases — follicular, ovulatory, and luteal. Predict next period date, PMS window, and cycle regularity from your average cycle length.
The Menstrual Cycle Tracker Calculator helps you understand and predict your cycle phases. By entering your last menstrual period (LMP) date and average cycle length, you can see when each phase of your cycle occurs: menstruation, follicular phase, ovulation window, and luteal phase.
Understanding your cycle phases helps you anticipate PMS symptoms, plan for your fertile window, and identify irregularities that may warrant medical attention. The average menstrual cycle is 28 days, but normal cycles range from 21 to 35 days in adults.
This calculator also projects your next 6 periods and PMS windows, so you can plan ahead for travel, events, and activities. Whether you are a beginner or experienced professional, this free online tool provides instant, reliable results without manual computation. By automating the calculation, you save time and reduce the risk of costly errors in your planning and decision-making process. This tool handles all the complex arithmetic so you can focus on interpreting results and making informed decisions based on accurate data.
Cycle tracking empowers you to anticipate your body's patterns. Knowing when to expect PMS, menstruation, and fertility can improve daily planning and reduce anxiety. It's also valuable medical information — irregular cycle patterns can be early indicators of PCOS, thyroid disorders, or perimenopause. Having a precise figure at your fingertips empowers better planning and more confident decisions.
Cycle Day = (Today − LMP) mod Cycle Length + 1 Phases: • Menstruation: Days 1–(period length) • Follicular: Days 1–(Cycle Length − 14) • Ovulation Window: (Cycle Length − 16) to (Cycle Length − 12) • Luteal Phase: (Cycle Length − 13) to Cycle Length • PMS Window: ~7 days before next period Next Period = LMP + Cycle Length Luteal Phase = Cycle Length − Ovulation Day Ovulation Day ≈ Cycle Length − 14
Result: Current: Day 12 (Follicular) | Next Period: March 1 | PMS: Feb 22–28
Assuming today is February 12: Cycle day 12, in the late follicular phase. Ovulation is expected around day 14 (February 15). The luteal phase starts after ovulation and lasts ~14 days. Next period expected March 1. PMS symptoms may begin around February 22 (7 days before the next period).
The follicular phase begins on the first day of menstruation and continues until ovulation. During this phase, the pituitary gland stimulates growth hormone (FSH) production, which drives follicular development in the ovaries. Estrogen rises progressively, thickening the uterine lining and triggering the LH surge that causes ovulation.
The luteal phase begins after ovulation and lasts until the next period. The ruptured follicle becomes the corpus luteum, which produces progesterone to maintain the uterine lining for potential embryo implantation. If pregnancy does not occur, the corpus luteum degenerates, progesterone drops, and menstruation begins.
Consult a healthcare provider if you experience cycles shorter than 21 days or longer than 35 days consistently, missed periods (while not pregnant), extremely heavy bleeding (soaking a pad/tampon hourly), severe pain that interferes with daily activities, or bleeding between periods. These symptoms can indicate treatable conditions.
The menstrual cycle has four phases: (1) Menstruation (bleeding, days 1–5), (2) Follicular phase (days 1–13, overlaps menstruation), during which estrogen rises and follicles develop, (3) Ovulation (about day 14), when the egg is released, and (4) Luteal phase (days 15–28), when progesterone rises to prepare for potential implantation. The total cycle length and phase durations vary between individuals, with 21-35 days considered normal for adults.
A cycle is considered irregular if it varies by more than 7–9 days from cycle to cycle, is consistently shorter than 21 days or longer than 35 days, or if you skip periods entirely. Occasional variation is normal, but persistent irregularity may indicate PCOS, thyroid disease, or other hormonal conditions.
PMS is caused by hormonal fluctuations during the luteal phase, particularly the drop in progesterone and estrogen before menstruation. Serotonin levels also fluctuate with these hormonal changes, contributing to mood symptoms. About 75% of women experience some PMS symptoms, with 3–8% having severe symptoms (PMDD).
Yes. Teenagers often have longer, more irregular cycles (up to 45 days). Cycles become more regular in the 20s and 30s, averaging 28 days. In the late 30s and 40s, cycles may shorten slightly before becoming irregular again during perimenopause. The typical cycle length decreases by about 1 day per decade.
Absolutely. Exercise during menstruation is safe and may actually help reduce cramps, bloating, and mood symptoms through endorphin release. Light to moderate exercise like walking, yoga, or swimming is well-tolerated. Some athletes adjust training intensity by cycle phase, with higher-intensity training during the follicular phase.
Hormonal birth control (pills, patches, IUDs) alters natural cycle patterns. Combined oral contraceptives suppress ovulation entirely, creating an artificial 28-day cycle. After stopping hormonal contraception, it may take 1–3 months for natural cycles to resume. This calculator is designed for natural (non-hormonally-controlled) cycles.