Apps and tools for conception

There are many apps, tools and kits on the market to help women predict when they ovulate. Here is an overview of the most popular methods used by these tools to predict ovulation.

Do ovulation predictor kits and tools work?

There is not enough evidence to say for certain that ovulation predictor kits, apps and tools help people get pregnant. This page tells you about the methods that are used by some of the apps and tools that are available.

Apps and tools are not regulated so you should proceed with caution if you decide to use one. Always read about how it claims to tell you your fertile window first. 

Having regular, unprotected sex (every 2 to 3 days without contraception) will give you the best chance of a successful pregnancy. Read more about this in our information about timing sex for pregnancy.

How to tell you are ovulating 

Your body goes through certain changes when you ovulate. 

  • Hormone levels change
  • Your temperature increases slightly
  • You have an increase in cervical mucus
  • Your saliva pattern changes.

Most of the apps or tools on the market use one or more of the methods below. If you’re using one, it’s important to use one that tells you how it calculates your fertile window. 

Be wary of apps that only use dates as this does not give very accurate results.

Measuring the level of luteinising hormone (LH) in urine

There is always a small amount of a hormone called the luteinising hormone (LH) in your urine but it increases once a month around the time you ovulate. This increase is known as the LH surge.

Ovulation test kits measure when this happens, giving you a ‘fertile window’ so you can make sure you have sex (and therefore sperm in your system to meet the egg) at this point.

Some tests also measure another hormone called estrone-3-glucuronide (E3G). This is produced when estrogen breaks down in your body and accumulates in your urine around the time you are ovulating.

Measuring your basal body temperature (temperature method)

Your basal body temperature is the temperature at which your body rests. This temperature is a bit lower than your “normal” temperature. It increases slightly when/after you ovulate.

If you track the increase over a few months you may be able to predict when you are next about to ovulate. However, it should be combined with other methods. By itself it is not recommended as a reliable way of telling whether you are ovulating.

  • It needs to be taken when you are most rested (just after you wake up).
  • It should be taken the same time every day (so you might need to set your weekend alarm to the same time as weekdays).
  • You need a very accurate basal thermometer.
  • It tells you after you have ovulated (too late for the sperm to be in your system).

Taking your temperature in this very exact way every morning can be tricky and because of this there is a danger of inaccuracy.

Temperature accuracy can also be affected by the following: fever, alcohol, emotional or physical stress, sleep disturbance, change of room temperature, change of waking time and change of climate.

Tracking the dates of your period (calendar method/rhythm method)

There are many apps that take your last period start and end dates and forecast your fertility based on these

You normally have a dashboard that displays your cycle. After using it for a while the apps learns your personal pattern and hope to improve their forecast with each cycle.

Using this method alone is not recommended as it is not very accurate, even for those with a regular cycle. It’s not uncommon for women with a regular cycle to have periods that vary by a few days each time.

Cervical mucus changes (cervical mucus method)

The cervical mucus method is all about examining your cervical mucus (vaginal discharge) to track its consistency. Your cervical mucus changes in amount and consistency throughout your cycle.

When you are ovulating the cervical mucus changes to become more wet and stretchy to help sperm move easily through the cervix into the uterus.

Getting to know your cervical mucus means becoming comfortable with looking at and touching your vaginal discharge.

The apps that track cervical mucus don’t actually check the mucus for you but they do help you by logging the consistency and tracking changes over time, which helps you become more aware of your cycle.

Most apps that track cervical mucus also track other symptoms.

Saliva ovulation predictor kits

These test for increased levels of oestrogen and salt in the saliva, which happens when you’re close to ovulating. You put some of your saliva on a glass slide, allow it to dry and look at the pattern if it makes. If it forms a fern-shaped pattern (known as saliva ferning) you may be ovulating.

Do ovulation predictor tools/kits work with PCOS or other fertility issues?

In some cases, for example in people with an anovulatory disorder (where you do not ovulate) the surge in LH may happen without ovulation. Talk to your GP if you have been testing your hormone levels for a few months and the results seem odd or are not showing ovulation.

Ovulation predictor tools may not be suitable if you have a known fertility issue that affects your menstrual cycle, such as polycystic ovary syndrome (PCOS). This is because this condition affects your hormones, so you may not get an accurate reading. Talk to your GP if you have PCOS and want to get pregnant.

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Johnson S et al. (2018) Can apps and calendar methods predict ovulation with accuracy? Current Medical Research and Opinion, 34:9,1587-1594, DOI: 10.1080/03007995.2018.1475348

NICE (2013). Fertility problems: assessment and treatment. National Institute for health and care excellence

Review dates
Reviewed: 22 November 2023
Next review: 22 November 2026