The Calendar Method
(Calendar Rhythm Method)

You can use the Calendar method (Calendar Rhythm method) to predict your most fertile time of the month and plan for pregnancy.

If you have been dutifully tracking your menstrual cycles, now is the time to put your written records to good use.

You have tracked your cycles for at least six to eight months. You have recorded all the first days of your menstrual cycles. Now from the statistics collected, you will be able to work out the number of days there are in your shortest and longest menstrual cycles.

This is important because the Calendar method predicts your fertile phase by roughly calculating the number of infertile days you have before ovulation (pre-ovulatory infertile phase) and after ovulation (post-ovulatory infertile phase) based on your shortest and longest cycles. As your cycle length varies from month to month, so do your fertile days.

The length of your pre-ovulatory infertile phase is calculated by subtracting 18 days from the total number of days in your shortest cycle. The length of your post-ovulatory infertile phase is calculated by subtracting 11 days from the total number of days in your longest cycle. Then, the fertile phase is calculated from 18 days before the end of your shortest cycle through 11 days from the end of your longest cycle.

Confused?

All right, let's see how the Calendar method formula works with some concrete examples:

Example 1:

If your shortest cycle is 22 days and longest cycle is 27 days:

Step 1: 22 -18 = 4 (pre-ovulatory infertile phase)
Step 2: 27 -11 = 16 (post-ovulatory infertile phase)

Your fertile window will last from Day 4 to Day 16.

Example 2:

If your shortest cycle is 30 and longest cycle is 36:

Step 1: 30 - 18 = 12 (pre-ovulatory infertile phase)
Step 2: 36 - 11 = 25 (post-ovulatory infertile phase)

Your fertile window will last from Day 12 to Day 25.

So there you have it!

Is the Calendar method accurate?

The truth is, the Calendar method is considered obsolete because of the emergence of better methods, techniques, tools and aids that are more accurate in ovulation predictions (please see "Related Links for Current Methods of Ovulation Prediction" below).

Modern techniques of ovulation prediction rely on several physiological fertility signs and the use of various tools and aids to help estimate the fertile phase, rather than just relying on the simple counting of days.

Introducing A Helpful Visual Aid!

Before we end off this page, there is something that you may like to see.

The Pregnancy Wheel is a visual and adjustable ovulation calendar that can predict your fertility regardless of whether you're having long or short cycles! In fact, this simple but amazing wheel can tell you a whole lot of info from fertility, to conception to delivery! So don't miss it, have a look here!

Related Links for Current Methods of Ovulation Prediction are:

• Signs of Ovulation
• Basal Body Temperature
• Ovulation Predictor Kit
• Saliva Ovulation Test Kit
• Fertility Monitor
• Fertility Charting Softwares

Return from Calendar Method to Menstrual Cycle

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