The Ovulation Calendar Method is also popularly known as the Rhythm Method, The Ovulation Roulette or simply The Calendar Method. It is a natural family planning method which involves knowing your fertile and unfertile days based on your usual ovulation cycle. Using these methods you can determine the “safe” and “unsafe” days for you if you are avoiding to get pregnant. During safe days, you can have unprotected sex without having to worry about getting pregnant because you are very unlikely to ovulate. During unsafe days, it is best to abstain from sex or simply use a backup family planning method like the barrier method.
Establish Your Range
A woman’s menstrual cycle is determined by counting from the first day of your menstruation to the first day of your next menstruation. The first step is to count your menstrual cycle duration for a minimum of 6 months. Regular menstrual cycle lasts usually from 26 to 30 days. In this case, you must get the average of your 6 months menstrual cycle. Irregular cycles are more variable in duration and lasts from 25 to 35 days. Knowing if your cycle is regular of irregular is important because there are different formulas for each of them. Irregular cycles have fewer “safe” days.
Do the Math
For those who have regular cycles, get the average of your cycle. Ovulation happens 14 days before your next menstruation. Ovums are susceptible for fertilization for 18 – 24 hours only while sperms live up to 72 hours. The general principle is you must abstain 5 days before and 3 days after your ovulation. According to the Ogino-Knaus formula, you must subtract 14 from your computed average. For example, your average cycle is 28. Subtract 14 and you get 14. Subtract another 5 from 14 and you get 9. Add 3 to 14 and you get 17. You are “unsafe” from days 9 to 17. For those who have irregular menstruation, for example your cycle ranges from 26 to 33 days. According again to the formula, you must subtract 18 from your shortest cycle and subtract 11 from your longest cycle. This makes your “unsafe” days, days 8 to 22. Ovulations of those who have irregular cycles are generally more variable which makes it more difficult to predict which particular day they ovulate.
Is this Applicable to You?
Women who have just started their menstrual cycle and whose cycles have become less frequent than usual should take caution because they may not be ovulating yet or may not be ovulating regularly anymore. This method is very difficult to perfect. It requires a very good, accurate and continuous recording of your past menstrual cycles. To use this, you also must have discipline regarding abstaining or using backup methods during “unsafe” days. A lot of will power is definitely required.