How to use your ovulation calendar
Enter the first day of your last period, your average cycle length and how long your period usually lasts, then click Build My Calendar. Instead of a single predicted date, you'll see six full months laid out with every day colour-coded: your period days, your fertile window, your ovulation day, and your PMS window, all projected forward from your own cycle pattern.
This is especially useful if you're trying to conceive and want to plan around travel or work commitments, or if you simply want a bigger-picture view than a single-cycle calculator gives you. For a single-cycle deep dive with more detail on fertility signs, see our ovulation calculator.
Understanding the colour coding
Purple: period days. Based on your entered period duration, starting from each projected period start date.
Teal: fertile window. The 5 days before ovulation plus ovulation day itself, when conception is possible.
Pink dot: ovulation day. The single day within the fertile window when the egg is actually released, giving the highest chance of conception.
Amber: PMS window. The 5 days before your next period, when oestrogen and progesterone drop and PMS symptoms are most likely.
Why your fertile window starts before ovulation
It's a common misconception that the "fertile" part of your cycle is just ovulation day itself. In reality, sperm can survive in the reproductive tract for up to five days, which means intercourse several days before the egg is even released can still result in pregnancy. That's why the calendar marks the five days leading up to ovulation, not just the day itself, as fertile.
The egg, once released, only survives for 12 to 24 hours: which is why ovulation day and the day before it are typically the two highest-probability days for conception within the wider fertile window.
Ovulation calendar with irregular periods
This calendar, like most calculators, assumes your cycle length stays fairly consistent from month to month. If your cycles vary by more than 7 to 9 days, common with PCOS, perimenopause, or high stress, the projected dates further into the six-month view will drift further from reality with each cycle, since small errors compound over multiple projected cycles.
If that sounds like your cycle, treat the later months on this calendar as a rough guide rather than a precise prediction, and re-run the calculator once your most recent period actually arrives so you're always working from your latest real data point. Our irregular period calculator is built specifically to handle cycles that don't follow a fixed pattern.