Health & Fitness
Predict your ovulation, fertile window and next periods with a cycle calendar and future projections.
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Enter the first day of your most recent period.
Set your average cycle length (the days from the start of one period to the start of the next — 28 is typical) and your usual period length.
Read your predicted ovulation day, fertile window, and next period in the summary and sidebar.
Browse the colour-coded calendar month by month, and use the next-six-cycles table to plan ahead. Copy or print your dates for reference.
Whether you're trying to conceive or simply want to understand your body's rhythm, knowing when you ovulate changes everything — because there are only a handful of days each cycle when pregnancy is possible. This tracker predicts your ovulation day, your fertile window, and your upcoming periods from three simple inputs: the first day of your last period, your average cycle length, and how long your period lasts. It then lays it all out on a colour-coded calendar you can page through month by month.
The science it's built on is the luteal-phase rule: ovulation typically occurs about 14 days before your next period starts, regardless of how long your overall cycle is. From that, the fertile window is the five days leading up to ovulation plus ovulation day itself — a six-day span that reflects how long sperm survive (up to five days) and how long the egg remains viable (about a day). Timing intimacy across that window is the single most effective thing you can do when trying to conceive, and the calculator highlights it clearly on every month.
You also get a plain-language cycle summary, a table projecting your next six cycles, and quick day counts to your next ovulation and next period. It's genuinely useful for planning — but it's a prediction from averages, not a certainty. Real ovulation moves with stress, illness, travel, weight changes and conditions like PCOS, so the calendar is a guide, not a contraceptive. For anyone avoiding pregnancy, relying on fertile-window predictions is risky; use a proven method and speak to your doctor. Ovulation test kits confirm the prediction with hormone data when timing really matters.
Timing intercourse during the fertile window when trying to conceive.
Predicting when your next few periods will start so you can plan around them.
Understanding your cycle pattern and spotting your most fertile days at a glance.
Keeping a simple visual record of period, fertile and ovulation days on a calendar.
Your fertile window spans about six days — the five days before ovulation plus ovulation day — because sperm can survive up to five days.
For the best chance of conceiving, aim for intimacy every 1–2 days across the fertile window rather than trying to pinpoint a single day.
Track a few cycles to find your true average length; predictions get more accurate the better your inputs reflect reality.
Ovulation predictor kits (which detect the LH surge) and basal body temperature tracking can confirm the calendar's estimate.
Using this as birth control. Fertile-window prediction is unreliable for preventing pregnancy because ovulation timing varies — use a proven contraceptive method instead.
Assuming ovulation is always on day 14. That's only true for a 28-day cycle; it actually falls about 14 days before your next period, so a 32-day cycle ovulates nearer day 18.
Trusting predictions with very irregular or long cycles, or conditions like PCOS, where ovulation can shift unpredictably or not occur every cycle.
Calculate your Body Mass Index and see the WHO category.
Calculate your Basal Metabolic Rate using the Mifflin-St Jeor equation.
Estimate your daily water intake based on body weight and activity.
Calculate your daily calorie needs (TDEE) for maintenance, cut or bulk.