Ovulation Calendar

What Is an Ovulation Calendar?

Keeping an ovulation calendar just means keeping track of your periods and doing some simple calculations. The goal is to figure out your most fertile days, the days you’re most likely to get pregnant. Ovulation refers to the release of an egg from your ovary, which happens around the same time in each menstrual cycle.

Finding Your Fertile Days

Your most fertile days are approximately 18 to 11 days before your next period. There is a smaller window within that time when you are most likely to get pregnant, but an ovulation calendar isn’t precise enough to show the exact days.

Making a Calendar

Begin with a regular monthly calendar. Circle the day your period starts (the first day of bleeding). Continue doing this for eight to 12 months, so that you can get a good idea of the length of your menstrual cycle. Your cycle goes from the first day of bleeding until the day before your next period begins. Don’t just guess about your cycle length—-being a day or two off can make a difference!

Now, count the number of days in the shortest cycle. Subtract 18 from that number. Take the difference and, starting with the first day of your next period, count that many days forward and mark the calendar with an X. That gives you the first day you’re likely to be fertile.

Next, subtract 11 from the number of days in your longest cycle. Take the difference and, starting with the first day of your next period, count that many days forward and mark the calendar. This is the last day you’re likely to be fertile.

For example, if your shortest cycle was 27 days, subtracting 18 gives you nine. So nine days after your next period starts is your first likely fertile day. If your longest cycle was 30 days, subtracting 11 gives you 19. Nineteen days after your next period starts is your last likely fertile day.

What if I’m on the Pill or the Patch?

If you’re using a hormonal method of birth control, like the pill, the patch, or Depo-Provera, the hormones in your medication are determining when you get your period. You’ll need to stop all forms of hormonal birth control before beginning to make your ovulation calendar.

How Do I Use My Ovulation Calendar?

If you’re trying to get pregnant, be sure to have intercourse during your fertile period—-as often as you can or want!

If you’re trying not to get pregnant, either avoid intercourse entirely during your fertile period, or use a barrier method like a condom or diaphragm. However, ovulation calendars are not considered a reliable method of birth control. Ovulation simply is not completely predictable. Of 100 women who use the calendar method as birth control for one year—without a single mistake—nine will become pregnant.

Women whose cycles are always less than 27 days should not rely on calendar estimates at all. Women with very irregular periods also have irregular ovulation times, which makes the calendar method unreliable.

How Can I Get More Accurate Information About My Fertility?

There are other, fairly simple methods of figuring out when you are likely to be fertile. You can look for changes in your body temperature and vaginal mucus or purchase an ovulation predictor kit that looks for certain hormones in your urine. Check out the LoveToKnow articles on Ovulation Predictors and Signs of Ovulation.

For More Information

• Information from Planned Parenthood on charting your fertility patterns
• Information from the National Women’s Health Information Center on fertility awareness

Additional Articles

• Ovulation
• Trying to Conceive
• How to Get Pregnant
• Ovulation Calculator
• Ovulation Predictors