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Birth Control: What Is The Calendar Method?

The calendar method is a popular option for natural family planning.
by Liana Smith-Bautista
November 25, 2018
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Choosing a birth control or family planning method is a very personal decision that must take several factors into account. If you decide against using a hormonal, barrier, or intrauterine device or substance and prefer to stick to natural solutions, this is absolutely your choice. And the calendar method is one of the most popular of these.

But as with most other family planning methods, the rhythm method’s effectiveness is reliant on how well you follow instructions. Part of ensuring you do this correctly is understanding how the calendar method works and why it may or may not be best for you.

Below are a few FAQs about the calendar method.

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What is the calendar method?

The calendar method of contraception is a type of fertility awareness method (FAM), meaning it involves tracking your ovulation so as to prevent pregnancy. Ovulation is when your ovaries release an egg, approximately once a month. It is one of three FAMs, the others being the temperature and cervical mucus methods. As the name suggests, the calendar method involves tracking your menstrual cycle on a calendar.

Note that to ensure maximum effectiveness through natural contraceptive methods, you may want to use the symptothermal method, which is a combination of all three FAMs.

Are there different calendar methods? How do they work?

Your fertile days are the days you’re most likely to get pregnant. They encompass your ovulation period and the days immediately before and after. To prevent pregnancy, either abstain from vaginal intercourse during this time or use other methods of contraception, like condoms.

The calendar rhythm method

The calendar rhythm method, often simply called the calendar method, requires rigorous tracking of your menstrual cycle. You’ll need to chart the number of days in your menstrual cycle for several months (at least six to twelve cycles are recommended). You’ll need to record the first day of each period and not the number of days between them. You’ll then have to plan intercourse carefully around your fertile period.

Here’s how to determine your fertile period using the calendar rhythm method:

First day of fertile period = Total number of days in your shortest cycle – 18
Last day of fertile period = Total number of days in your longest cycle – 11

Thus, if your shortest cycle is 25 days and your longest is 30 days, your calculation would look like this:

First day of fertile period = 24 – 18 = 6th day
Last day of fertile period = 30 – 11 =19th day

For more on this method, check out the article on the rhythm method at

The Standard Days Method

The Standard Days Method, which is a variation of the calendar method, also requires tracking your menstrual cycle for several months in order to determine how long your cycle lasts. But this method will only work if your cycle falls within the range of 26 and 32 days. If it is longer or shorter, you’ll need to use a different method to track your ovulation. If your cycle is in this range, your fertile days fall between days 8 and 19; you’ll need to abstain or use other birth control during this time.

How effective is the calendar method?

According to Planned Parenthood, the different fertility awareness methods range between 76 and 88 percent effectivity, in comparison to the upper-90-percentile effectiveness seen by methods like the Pill, condoms, and so on.

For better contraception, combine the calendar method with the temperature method (where you take your temperature each morning) and the cervical mucus method (where you check your vaginal discharge, or cervical mucus, daily).

You’ll also be more successful if you work closely with your doctors and make sure you have a thorough understanding of each process.

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I have irregular periods. Can this affect how successfully I use this method?

If the variations in your period fall within the normal range (24 to 38 days), you can still use the calendar rhythm method. Only use the Standard Days Method if your cycle is between 26 and 32 days long. Just make sure you speak to your doctor so you can tailor your tracking to their recommendations.

What other factors make the calendar method less effective?

Because it is highly reliant on cyclical information, the calendar method can become less effective with poor tracking (like incorrect charts) or changes in your menstrual cycle. Variations in your cycle may result from stress, illness, miscarriage, or a change or the dosage of hormonal medication.

Are there tools or apps that can help with this method?

Rhythm beads are often used to help track fertile days using the calendar rhythm method. There are also several mobile, web, and desktop applications that make the charting process more convenient.

What are the pros and cons of using this method?

Pros: If you are concerned about putting foreign substances or devices into your body, you can rest easy with the calendar method. You may also find that this method is compatible with certain religious beliefs or practical philosophies, where others may not be.

Cons: The calendar method is completely reliant on your ability to consistently track your menstrual cycle and your willpower to either abstain from vaginal sex or use other methods on your fertile days. If you are prone to forgetfulness or enjoy spontaneity in your sex life, this can become problematic. It may also prove unreliable if there are other factors affecting your menstrual cycle, like delayed or early periods due to stress, illness, and so forth.

Is the calendar method right for me?

Only you can answer this, with the help of your gynecologist. We recommend checking out our article “Which birth control method is right for me?” so you can educate yourself on the alternatives to the calendar method. This way you can make an informed decision after learning about all the contraceptive methods available to you.

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