Stress and other factors can result in more phases with more thin cervical mucus. If ovulation has already occurred, you can only then determine this in retrospect on the basis of higher temperature measurements.

Calculating ovulation = find your fertility time window

The time around ovulation is the only time during the menstrual cycle when a woman can become pregnant. Thus, it makes sense for a couple trying to have children to know when this occurs.

Try our ovulation calendar widget as a rough guide to help you track your ovulation. Some people also refer to this as an ovulation calculator.

In addition, several other methods are explained below, which will help you track your ovulation, i.e. your fertile time window.

The Top 6 Methods

Method 1 – Use our ovulation calculator widget

For women who have a normal 28 to 32 day menstrual cycle, ovulation can take place anytime between day 11 and day 21. Remember this is just an average — every woman’s cycle is different!

Try the calculator now to get an idea of your ovulation time window this month. Keep in mind that this is just a very rough statistical approximation and the exact day needs to be confirmed with the other below techniques.

Calculate ovulation

First day of your last period

Length of your cycle

Why is this information useful?

  • If you are actively trying to conceive (TTC) you know when to have lots of intercourse: the ideal frequency is the night before ovulation, the morning of ovulation day, again at night of ovulation day and a fourth time the morning after ovulation day.
  • If you are avoiding to get pregnant knowing when you are likely to ovulate will help you decide when to avoid intercourse. This will reduce your chance of getting pregnant. There are of course plenty of other ways to be intimate with your partner without intercourse.

Method 2 – Measure your basal body temperature

After ovulation, the female body releases a hormone called progesterone. Its role in the body is to ensure that there is a good blood supply to the uterus in order to successfully maintain a possible pregnancy. A side effect of progesterone is that it causes body temperature to increase by as much as 0.6°C1. Body temperature remains at this level until the start of menstruation, and subsequently drops. Women can make use of this information to determine when they ovulate.

You should follow these five rules in order to determine your fertile days accurately via body temperature:

  • Always measure in the morning straight after you have woken up, when you are still lying down.
  • If possible, measure in the same spot and at the same time every day.
  • Measure for at least three minutes rectally, vaginally or orally, and keep the type of measurement the same during a cycle.
  • Make sure that you have slept for at least six hours before measuring your basal temperature.
  • Start the list or graph on the first day of your period, which is also the start of your menstruation cycle.

Creating a temperature curve

After measuring your temperature note down the value in a list or as a point on a graph. Also make a note of any irregularities that occur: less sleep, illness, stress, medication and alcohol on the day before the temperature measurement.

This is because the basal body temperature will be influenced by many factors. Join up the individual points on the graph. If you have missed out a measurement, leave a gap for that day.

Because the temperature measurements at the beginning of the cycle sometimes vary drastically, you can ignore the first four values in your analysis.

Now examine the values from the low temperature phase after the fifth day. For a better overview, you can draw a horizontal line directly above the highest values (excluding outliers).

Then check whether there is a sudden rise in temperature of at least 0.2°C in the low values of the first half of the cycle. The rise should occur within the space of two days.

If the temperature is higher than the value in the low temperature phase on at least three consecutive days, you can assume that ovulation took place in the 48 hours before the rise in temperature.

The second half of the cycle usually lasts from day 12 to 16. This can help you when interpreting your temperature curve. The rise in temperature should occur around two weeks before the onset of menstruation for the following month.

Types of curve

There are many variations between temperature curves and one rarely corresponds to the ideal shape. Also small variations can complicate the interpretation of the curve. However, when you have monitored your basal temperature for a few months, you will have had more practice at analysing the temperature. This means that you can accurately forecast your fertile days after a few cycles.

From the experiences of previous cycles you can also reach conclusions for the following months. This can narrow down the period of time during which ovulation may occur. For very irregular cycles, this may be difficult.

Different phenomena can be observed when determining fertile days using the temperature curve. Above all, if your period is late or the bleeding is considerably lighter than usual, it may be a possible indication that you are pregnant. Other factors can also be responsible for the constantly raised temperature, such as febrile illnesses.

  • During the first half of the menstrual cycle, one value for temperature is significantly higher than all of the rest: This can be due to for example, alcohol consumption the evening before, a cold, fever, stress, or going to the toilet several times before measuring temperature. Highly unusual readings should be disregarded, otherwise they can confuse your interpretation of the temperature curve.
  • During the second half of the menstrual cycle, one temperature value lies on the same level as the low temperature phase: If the temperature sharply drops during the second half of the cycle on one or more days, this can suggest corpus luteum deficiency. This is most likely when it occurs for no apparent reason over several cycles. Some medications reduce the temperature, and can therefore distort the curve. Also measuring at a different time or in a different part of the body can be the reason for a single low temperature measurement.
  • Shortly before the sudden increase, the morning temperature falls again: The decrease shortly before ovulation frequently occurs and is completely normal. Women who experience this are able to determine when their fertile days are even before ovulation.
  • The rise in temperature is not abrupt, but gradual: This indicates a slight corpus luteum deficiency. If the temperature rises only by 0.1°C for several days and only continues after this, corpus luteum deficiency is likely. This does not necessarily lead to a reduction in fertility.
  • The second half of the cycle is shorter than twelve days: If the time from ovulation to the next menses is less than twelve days, corpus luteum deficiency is the likely reason.
  • There is no increase in temperature: If an increased temperature level is not recorded during the second half of the cycle, ovulation has not occurred. Therefore in this cycle, you cannot become pregnant. An absence of ovulation despite regular cycles can be relatively frequent in older women. Also breastfeeding, a recent miscarriage, physical changes after no longer taking birth control pills, or hormonal disorders can cause a temporary anovulation.
  • The temperature falls at the end of the cycle: If the temperature suddenly drops to a low level again, this means that menses will happen soon.
  • The temperature remains high for more than 16 days despite menses: During the first days of the new cycle the basal body temperature sometimes remains elevated and sinks to a lower level by the 5th day at the latest. However the temperature remains elevated further when you are pregnant.

Method 3 – The cervical mucus method

While ovulation can be identified retrospectively on the basis of raised basal body temperature, the consistency and appearance of cervical mucus indicates impending ovulation2.

This is because in the fertile phase the uterine cervix produces especially runny secretions in order to facilitate the route of the sperm in the uterus. Women usually produce so much cervical mucus that they primarily discover it during their fertile phase when they clean with toilet paper.

Because ovulation is ultimately triggered by another hormone, luteinising hormone (LH), high mucus secretion is not absolute proof of ovulation. Therefore it is recommended to judge whether ovulation has occurred through a combination of the examination of cervical mucus and the temperature measurements. On the temperature graph the consistency of the secretion can be noted on a daily basis.

Usually, a woman needs a few months in order to accurately interpret the consistency of the cervical mucus. However after this, observations and experience can give a good indication of when the fertile phase occurs.

Learning to interpret cervical mucus

  • During menstruation, the cervix secretes hardly any cervical mucus.
  • In the following days you can usually find lumps of mucus, which are tough and rubbery. Their shape is hardly changed when they are pulled apart using two fingers.
  • Over time more mucus appears, and it can now be pulled apart far between two fingers. The secretion also becomes thinner and clearer.
  • At the beginning of the fertile phase, a few days before ovulation, a mucus strand may be stretched several centimetres without breaking. It is now almost transparent and it resembles fresh egg whites.
  • On the day before ovulation, on the most fertile day of the cycle, the cervical mucus is at the point where it can be pulled apart by the maximum distance that is possible during the entire cycle.
  • Shortly after ovulation the secretions become lumpy and tough again. The fertile phase has ended.

Stress and other factors can result in more phases with more thin cervical mucus. If ovulation has already occurred, you can only then determine this in retrospect on the basis of higher temperature measurements.

Examination of the cervix

Women who produce less cervical mucus can regularly feel the neck of their uterus and their cervix in order to determine when their fertile phase occurs. The cervix, which protrudes from the uterus into the vagina, opens around the time of ovulation. This creates an optimum condition for the sperm to penetrate.

During the infertile phase at the beginning of the cycle and after ovulation, the cervix lies deeply in the vagina. By using two fingers in a squatting or standing position, it can be felt easily. In this case it is relatively hard and closed.

In the days around ovulation the neck of the uterus and the cervix lie in a higher position. It is more difficult to feel them at this time using your fingers. The cervix opens, which is felt as a small dimple/pit, or a slit on the spherical structures. It also feels very soft.

The examination should be started at the end of menstruation. The position, the finger used and the time should ideally be kept the same throughout the whole cycle.

Important tip: wash your hands thoroughly before the examination, to avoid infections. Also if you empty your bladder first it is easier to feel the cervix.

Method 4 – Test sticks and strips

The level of the hormone LH (luteinising hormone) rises sharply at the end of the first half of the cycle, triggering ovulation. When the level of LH reaches its maximum, it indicates that it is around one day until ovulation occurs.

Test strips function on the same principle as pregnancy tests. Most ovulation sticks need to be kept in a woman’s urine for a short amount of time. After a few minutes, a control strip becomes visible. If the LH value is high, two lines will be shown.

The tests usually indicate when a woman is highly fertile. In this case, the intensity of the strip indicating the LH level will be at least as strong as the control strip. Since all ovulation tests work a little differently, you should carefully follow the manufacturer’s instructions.

When you know your body through the use of the temperature method and inspecting cervical mucus, you can identified possible ovulation dates. The test can be used over these few dates to confirm fertility.

An ovulation test specifically for women who have a very irregular cycle is particularly useful. This is because the temperature method only gives you a result that ovulation has occurred when the fertile phase has already passed.

Unfortunately in this case a lot of test strips are needed. You should start with the control around two days before your earliest possible ovulation date, and continue this until the observed LH surge.

Click to read our comparison of the best ovulation calculator kits

Method 5 – Cycle Computer

A cycle computer can be very useful in determining the fertile phase. The cycle computer uses exactly the same features for this – temperature3, LH-surge as well as progesterone-surge.

The advantage of using a cycle computer is that it can process the dates itself. Constructing the graph and analysing the values is already done for you.

The cycle computer is a useful addition in family planning. It can help identify the fertile phase for a couple trying to have a child.

Click to buy a cycle computer from Amazon

Method 6 – Smart phone apps

Last, but certainly not least there is a huge amount of fertility smartphone apps available for iPhone and Android.

These apps help women track their periods and health related issues – such as their weight and emotional and physical well being. Women can be sent reminders of their most fertile days and usually everything is organised in an easy and stylish calendar.

Many apps come free and some offer extra features if you pay for the Premium version. The trick is to know which ones are good and which ones to avoid.

Click to read our comparison of the best fertility apps

The perfect BMS / intercourse timing strategy

As discussed in the video above, the following BMS strategy will allow you to maximise your chances of getting pregnant each month:

  • at night before the day of ovulation
  • in the morning on the day of ovulation
  • again at night on the of ovulation
  • a fourth time the morning after ovulation day

Having frequent intercourse around the day of ovulation will allow for plenty of sperm to be present. This strategy maximises the chances that one sperm cell will reach the egg and fertilise it.

Male fertility supplements combine many key nutrients to create one powerful fertility-enhancing pill.

We have compared a number of products to help you decide which supplement to choose.

But this is not all:

Once the egg has been fertilised, it needs to implant itself in the uterus. For this to happen, numerous hormonal changes must successfully take place inside the female body. Also, numerous nutrients such as iron, folic acid and fatty acids must be present to enable the body to build a nutritious “nest” for the egg. Please continue by reading our dedicated article:


  1. Charkoudian N, Stachenfeld NS. Reproductive hormone influences on thermoregulation in women. Comprehensive Physiology. 2014. 4(2): 793-804
  2. Gross BA. Natural family planning indicators of ovulation. Clinical Reproduction and Fertility. 1987. 5(3): 91-117
  3. Gross BA. Natural family planning indicators of ovulation. Clinical Reproduction and Fertility. 1987. 5(3): 91-117

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