How to track ovulation: 5 ways to find your most fertile days

Trying for a baby can be an exciting and anxious time all at once. Once you’ve decided that you’d like to start a family, it’s natural to want to do all you can to maximize your chances of conceiving. 

You may have heard about your fertile window. Basically, this is the point in your cycle when you’re most likely to get pregnant. It’s true that having lots of sex around ovulation can boost your chances of getting pregnant. But how can you tell when you’re ovulating? Let’s take a closer look.

Key takeaways

• Your fertile window lasts for an average of six days each cycle, including the five days before ovulation plus the day after. 
• If you have a 28-day cycle (which is considered to be average), ovulation happens midway through your cycle on day 14. However, as normal cycles can range from 21 to 35 days long, the timing of when you ovulate can also vary from month to month, and it can be hard to pinpoint the exact day. 
• There are several methods to help you predict when you’ll ovulate, from analyzing your menstrual cycle and discharge to investing in tests and smart devices. You can also look for the signs and symptoms of ovulation. The best method — or combination of methods — comes down to personal preference and what suits you.

What is ovulation, and why does it matter?

Ovulation is when your body releases an egg in the hope that it will be fertilized by a sperm. It’s when you’re most fertile during your cycle and usually happens around the midpoint. That means that if your cycle is around 28 days long, then this happens on approximately day 14. 

Once an egg has been released from one of your ovaries, it travels down one of your uterine tubes. For the next 12 to 24 hours, it’s what doctors call “viable” or able to be fertilized. If you have sex during this time, a sperm might meet your egg in the tube and fertilize it. This is the part known as conception. If this happens, then your fertilized egg may travel down to your uterus and attach to the lining of the uterus — a process known as implantation. If this happens, then you’re officially pregnant. 

The 12-to-24-hour window, when your egg is still viable, might seem like a really short period. But your fertile window is actually much longer than that. This is because sperm can live in your body for up to five days. That means your fertile window spans around six days in total: the five days before ovulation plus one day after.

What are the main methods for tracking ovulation?

There are five main methods for tracking ovulation: the calendar method, tracking apps, ovulation kits, basal body temperature changes, and cervical mucus changes. 

If you’re trying to get pregnant, then the best place to start is to figure out when you’re likely to ovulate. This can vary from cycle to cycle and person to person. All this means is that knowing exactly when you’ll ovulate can be tricky. 

Using one or a combination of methods can help you spot the patterns and pinpoint when ovulation is most likely to happen for you. 

How does the calendar method work?

The calendar method, sometimes called the rhythm method, is when you calculate the length of your previous menstrual cycles to figure out which days could include your fertile window. It involves following these simple steps:

• Record the length of six to 12 menstrual cycles. This means counting the days between the first day of one period and the first day of your next period.
• Write down the lengths of your shortest menstrual cycle and your longest cycle. 
• Subtract 18 from the total number of days in your shortest cycle. This number represents your first fertile day. For example, if your shortest cycle is 28 days long, your first fertile day would be day 10. 
• Subtract 11 from the total number of days in your longest menstrual cycle. This number represents the last fertile day. For example, if your longest cycle is 34 days long, your last fertile day would be day 23. If you’re trying for a baby, it may be the best time to schedule some conception sex during your possible fertile days, which in the example above would be between days 10 and 23. 
• Keep updating your calculations each month. The more up to date you are, the better. 

“For those who have a predictable menstrual cycle, the calendar method can be a very reliable way to track ovulation,” says Dr. Renita White, obstetrician and gynecologist (OB-GYN), Georgia Obstetrics and Gynecology, Georgia, US. “Predictable cycles mean that you can determine when your next period will be each month.” 

You might have also heard of the calendar method called the standard days method. This is incredibly similar with a slight variation and works best if your cycles are usually between 26 and 32 days long. The idea is that if your cycles are always this regular, your fertile days should land between days eight and 19. 

As many factors can impact the timing of ovulation, from illness to stress, these methods of tracking ovulation aren’t always accurate, especially if you have irregular periods. However, they can be a great place to start and are totally free.

How do cycle-tracking apps predict ovulation?

When you use a menstrual cycle and ovulation-tracking app like Flo, all you need to do is log your period dates for a couple of cycles, then an algorithm will predict your ovulation days for you.

“These tracking apps make it easy to look back and review patterns each month,” says Dr. White, OB-GYN. “Not only can you see how often you get a period, but you can also see when you typically get certain symptoms. This can make it easier to identify your ovulation window.”

With Flo, you can easily log these symptoms and learn more about why they happen, so you’ll become a pro at spotting your likely fertile window in no time. You can also log your basal body temperature (BBT) and ovulation test results, keeping all that important ovulation information in one place. Try Flo for free now. 

How accurate are ovulation prediction kits?

If you use them correctly, ovulation prediction tests can be up to 99% accurate. 

These kits can take the guesswork out of tracking ovulation by confirming when you’re about to release an egg. For some people, this level of certainty can help reduce the anxiety around trying for a baby, while others may find it adds to the pressure. Everyone is different, and it’s about finding what feels right for you. 

So, how do ovulation kits work? Well, the tests look for luteinizing hormone (LH), which is the hormone that makes your ovaries release an egg. LH surges 24 to 48 hours before you ovulate. So by detecting this surge, ovulation tests can tell you when it might be best to have conception sex. “Some tests also detect estrogen levels, which also increase around ovulation with the goal of being more accurate,” adds Dr. White, OB-GYN. 

Like home pregnancy tests, ovulation kits involve peeing on a stick to measure your hormone levels. To pick up the LH surge, you might need to keep testing for several days (the packs usually come with around five to seven sticks). As a general rule, you should start testing three to five days before you think you might ovulate.

How does basal body temperature show ovulation?

When you ovulate, your basal body temperature (BBT), which is your temperature when your body is completely at rest, increases by a small amount: between 0.4°F and 1°F (0.22°C and 0.56ºC). So, measuring your BBT every day using a special thermometer with two decimal places can help you learn when you tend to ovulate. 

“To best use this technique, it’s ideal to track your temperature for a few months to determine the typical time your basal body temperature increases,” says Dr. White, OB-GYN. 

For the most accurate readings, you should:

• Take your temperature as soon as you wake up, around the same time each day, and before you get out of bed. 
• Make sure you have had at least three hours of uninterrupted sleep before taking a reading. 
• Make a note of when you’ve had a fever or been unwell, drunk alcohol, been stressed, had a bad night’s sleep, overslept, or traveled in a different time zone. These factors can influence your BBT and make your readings less accurate. 

Measuring your BBT with a thermometer each day can get fiddly and feel like a chore, especially if you’re not a morning person. Thankfully, you can now buy wearable devices with built-in sensors that will measure BBT for you. Often, these devices can pair with Flo, helping you bring all your cycle information together.

What does cervical mucus tell you about ovulation?

Right before and during the day of ovulation, your discharge (also called cervical mucus) will turn clear and slippery, a bit like raw egg whites. This is to help make it easier for sperm to swim through your reproductive tract and meet an egg. Clever, right?

The egg white discharge usually lasts for about four days, signaling that it’s time to have unprotected sex if you’re trying. 

Throughout the first half of your cycle, before you ovulate, the cervical mucus will be thick, white, and dry. After ovulation, your discharge will become dry until you get your period a couple of weeks later. 

“Though it is common for people to have these changes around ovulation, some people may have a hard time noticing the changes to the cervical mucus,” says Dr. White, OB-GYN. “Others may have ovulation-type cervical discharge for longer periods of time. Being on certain medications like birth control can also affect what your cervical mucus looks like.”

A change in your cervical mucus isn’t the only possible sign of ovulation that you’ll notice. Some people experience symptoms of ovulation pain such as cramping, heightened sex drive, bloating during ovulation, mood changes, and light bleeding around the time of ovulation. 

Keeping an eye out for the signs of ovulation and tracking them in an app like Flo can help you get to know the pattern of your most fertile days. 

What’s the best method for tracking ovulation?

“The most accurate method is an ovulation kit since it detects the presence of hormones that spike before ovulation,” says Dr. White, OB-GYN. However, while ovulation tests are up to 99% accurate when used correctly, they can be expensive, and some might find the testing process stressful. 

Each method has its benefits and drawbacks. For example, the calendar method might suit some people best because it’s free, but it can be less useful for people who have irregular periods. 

Ultimately, there’s no “best method” for tracking ovulation. The right one will be personal to you. The best thing you can do is try out a few different methods and see how you like them. And remember, whichever type you choose, an app like Flo for Getting Pregnant can help you keep track of your cycle dates and symptoms as you go.