Determine Fertile Days

All about determining the fertile days for ovulation in order to get pregnant with sex at the optimal time. Necessary basic knowledge, literature, methods, cycle computers and more …

How many fertile days does a woman have per cycle?

fertile days

biological fertile days

The fertile window consists of both the viability of the sperm (5 days) and the one day at which the ovum is capable of fertilisation. If the egg and sperm meet, pregnancy may occur. Taking into account that sperm can wait about three to five days in the woman’s body for ovulation and the ovum is fertile for about 12 to 18 hours after ovulation, results in a biological fertile period of about 6 days. How to best determine and limit the fertile days is explained in the next section.

Determining fertile days – that’s worth knowing

cycle length

The biologically fertile days cannot be determined exactly with any method. Currently, it is not possible to determine perfectly the biologically fertile days with any method. This is mainly due to the fact that one cannot look into the future and the natural cycle is subject to more or less large fluctuations. For example, the cycle length of most women varies between 23 and 35 days. All natural methods or cycle computers usually give more fertile days than are biologically necessary. One speaks in this case of method-related fertile days.

Fertile days cannot be calculated with an ovulation calculator

Many women who want to become pregnant use ovulation calculators to calculate their fertile days. Unfortunately, the ovulation calculators are far too inaccurate. The cycle length and the time of ovulation may vary from cycle to cycle. For example, ovulation may be postponed by a few days or even longer due to external influences. One can determine the fertile days only by a day by day observation of certain body signs such as basal temperature, cervical mucus and cervix. Calendar methods or ovulation calculators are therefore very inaccurate and in most cases not particularly well suited for the determination of fertile and infertile days.

Which methods are best suited for determining the fertile days?

The 5 best methods to become pregnant and to determine the fertile days, are outlined in the following step by step instructions, in order to give you a good overview.

1st Place: The Symptothermal method

Symptothermal Method The Symptothermal method is best suited for determining fertile and infertile days. In this method, the signs of ovulation cervical mucus and basal body temperature are documented in the course of the cycle in a cycle sheet and then determined on the basis of solid method rules, the fertile and infertile days. In a comparative study by Stiftung Warentest, this method was able to beat every cycle computer.

2nd Place: Cycle computer

cycle monitor for ovulation tracking

Cycle computers are, in our opinion, the second best way to determine the fertile and infertile days. In a comparative study by Stiftung Warentest foundation, cycle computers for the production of children did worse than the self-applied Symptothermal method. However, the accuracy of the cycle computers is usually sufficient to limit the high fertility period for couples wishing to have children. In our opinion, there are currently two cycle computer types that can be recommended for the desire to have children. To a symptothermal cycle computer based on the Temperature method and Symptothermal method. In our opinion, the best cycle computer on the market is the Cyclotest MyWay, which I have tested for over a year. To the other hormone computer, which measures the body’s own hormones like the LH over a urine test and then subsequently issues the fertile days. The best cycle computer in this segment is the Clearblue Fertility Monitor, whose fertility display could really achieve very good results in studies for the highly fertile period.

3rd Place: Ovulation test

Ovulation Test - LH Test Ovulation tests are a simple and relatively inexpensive way to learn about the highly fertile time to ovulate. As a rule, ovulation tests are not other than special urine tests that measure the levels of the luteinising Hormones (LH). The LH is a sex hormone, which is strongly suspected of triggering ovulation and shortly before ovulation, the LH level is significantly increased. In this case, an LH test should theoretically be positive. In my Ovulation test Experience, however, LH tests do not work equally well for all women and all cycles. For this reason, I recommend these tests not as a single method, but in addition to the Symptothermal method or a cycle computer to use to determine the fertile days.

4th Place: Billings Ovulation Method

Billings Method The Billings method is an NFP method, which uses the sole observation of the cervical fluids in the course of the cycle, with fixed rules to determine the fertile and infertile days in the cycle. In our opinion, the Billings method is very suitable for couples with a desire for children, because the cervical mucus changes its appearance and its elasticity just before ovulation. One disadvantage of the Billings method is, in our opinion, the relatively complicated rules of the method. What’s more, unfortunately, you can not tell from the cervical mucus – if you really have/had an ovulation. Ovulation can only be determined by measuring the basal temperature or by daily ultrasound examinations. The latter would be practically impossible to implement. For these reasons, the Symptothermal method with mucus and temperature monitoring is more suitable than the Billings method.

5th Place: Temperature Method

temperature method In the Temperature method, similar to the Billings method, only one fertility sign is used for the determination of the fertile days in the cycle – namely the basal temperature measured in the morning. For three reasons, the only applied Temperature method is unfortunately not so well suited for pregnant women. First, due to the strict temperature rules, not all women can determine the fertile days in each cycle. In studies, women in only 52 per cent of the cycles studied were able to determine their fertile days according to the strict rules of this method. This is rather unfavorable if you want to become pregnant and you want to take advantage of each cycle. Secondly, the basal temperature usually only rises shortly after ovulation, which is of course rather unfavourable in the present child’s desire, because the optimal time for sex lies just before ovulation. Thirdly, in our opinion, it is too inaccurate if you only rely on a fertility sign to determine the fertile days. What if the temperature is disturbed or the half-cycle cannot be measured by an illness? Then it is much cheaper to have other signs of ovulation such as the cervical mucus or the ovulation tests or others available. Nevertheless, despite these weaknesses in The Temperature method, I am convinced that it belongs to the 5 important methods to determine the fertile days and brings a thousand times more than an ovulation calculator.


pregnancy rate fertility awareness

C Gnoth et. al. Hum Reprod. 2003 Sep;18(9):1959-66.

In my opinion, the methods listed here are really the best methods that exist in the world to determine the fertile and infertile days. The symptothermal method for me is the absolute No. 1, because so inexpensive and accurate you get the fertile days determined by no other method. The absolute plus, however, is the cycle diagnostics with which it is possible to clearly recognize cycle characteristics such as luteal insufficiency and basal body temperature, which may stand in the way of having children, and then treat them accordingly. Likewise, the method allows determining a pregnancy without a pregnancy test – only on the basis of the basal temperature curve. But the best part of all is that studies have proven beyond reasonable doubt that 81 per cent of couples use the fertility awareness methods to become pregnant in just 6 months. Without method, the pregnancy rate is only 60%. So, in any case, it’s a good idea to use the Symptothermal method and fulfil your biggest dream of bearing a child. For this reason, I recommend you the Get Pregnant Starter Set, by finding everything you need to start with the symptothermal method. I wish you all the best from the heart that you can fulfil your dream of the desired child as soon as possible. Observing the fertile days in the cycle was personally the key to success and I have become pregnant thanks to The Symptothermal method twice in the 1st cycle despite Hashimotos and luteal insufficiency.