Reading the calendar
Red days are your predicted period. The pink band is your fertile window: the five days before ovulation, when sperm can survive and wait for the egg, plus the day after. The purple day is predicted ovulation. Everything else is low probability, though not zero.
The grid repeats your cycle at a fixed length, so month one is the most trustworthy and later months are projections. When your next period arrives, come back and enter the new date; the calendar re-anchors from there.
Making it more accurate
A calendar predicts; your body confirms. Ovulation test strips started a few days before the pink band catch the LH surge that precedes ovulation by a day or so. A sustained rise in basal body temperature confirms it has happened. If your cycles vary by more than a few days, swap this page for the ovulation calculator for irregular periods, and read about the fertility awareness methods that combine these signs.
Frequently asked questions
How does the ovulation calendar work?
It takes the first day of your last period and your average cycle length, places ovulation 14 days before each predicted period, and colours the five days before ovulation plus the day after as fertile. Period days are shaded from each predicted start for the number of days you enter. The pattern repeats for as many months as you choose.
How accurate is an ovulation calendar?
As accurate as your cycle is regular. If your cycles vary by only a day or two, the first month is usually reliable and later months are close. If your cycles vary by a week or more, the calendar will drift; use the irregular-periods ovulation calculator for a date range and confirm ovulation with test strips.
Can I use this calendar to avoid pregnancy?
Not on its own. Calendar-based methods have a typical-use failure rate of around 12 to 24% per year because ovulation moves. If you want to avoid pregnancy, combine cycle tracking with a barrier method or another form of contraception.
Which days on the calendar are best for conceiving?
The two days before ovulation and ovulation day itself carry the highest chance. Sex every one to two days across the whole shaded fertile window covers the possibility that ovulation comes a little early or late.
Can I print the calendar?
Yes. The Print button hides the form and buttons and prints just the month grids and legend. The link in your address bar also keeps your inputs, so you can bookmark it and come back.
These calculators give estimates based on cycle averages and standard formulas. They are for general information only and are not medical advice. For anything concerning your health or pregnancy, talk to a qualified healthcare provider.