How Can You Know When It's Ovulation Day?

Using Cervical Mucus, Ovulation Predictor Kits, and BBT Charts

Ovulation calendar

Just about every person trying to get pregnant wants to know when it's ovulation day. This is the day an egg will be released from the ovary, and this is the day you want sperm waiting in the fallopian tubes available to fertilize that egg.

You are more fertile in the days leading up to ovulation. If you can have sex during this time, your odds of conceiving will go up considerably.

There are other reasons to know when you ovulated.

If you know the day you ovulated, you can count the days in your luteal phase and know when is the best time to take your pregnancy test. Knowing the day of ovulation may also help your doctor determine your due date. This is especially true if your cycles are irregular.

There are a variety of ovulation detection methods you can use to predict ovulation day: cervical mucus tracking, basal body temperature charting, cervical opening changes, ovulation test strips, and others.

You may need to try each one out until you find a method that fits your lifestyle and menstrual cycles.

What does your cervical mucus look like on ovulation day? What’s happening on your body basal chart when you’re ovulating? All of these answers are below.

Note: you don't have to know when your ovulation day is to get pregnant. If tracking ovulation stresses you out (and you’re not alone if it does), you can instead choose to have sex frequently all month long instead.

You’re bound to have sex during your fertile window if you ​choose frequent sex—instead of timed sex—instead. More on this below, too.

Determining Ovulation Day With Fertile Cervical Mucus

When you're not in the ovulation period, cervical mucus is thick and sticky, so it can trap bacteria and other intruders.

This includes sperm!  

As ovulation day approaches, your vaginal discharge changes. It will become more abundant and more like raw egg whites. This helps sperm swim their way up into the reproductive tract.

Once ovulation passes, the cervical mucus will dry up again and become sticky.

On ovulation day itself, your cervical mucus may be like raw egg whites. Typically, this very fertile quality cervical mucus will last for two or even three days. (These two to three days precede ovulation.)

However, sometimes, cervical mucus has passed its peak by the time ovulation day comes. You may have your most fertile quality discharge the day before you actually ovulate.

This is okay because you’re actually not the most fertile on ovulation day. Your most fertile day is the day before.

Research has found that having sex on days with abundant fertile cervical mucus is one of the best methods of timing intercourse for pregnancy. This was true even when ovulation didn’t exactly occur on the same days with the raw-egg-white mucus.

In other words, in this study, it didn’t matter when the couple had sex in relation to ovulation day itself. As long as sex occurred when there was fertile quality discharge, a couple’s odds of getting pregnant went up.

Tracking cervical mucus isn’t for everyone, though.

Some women just don’t notice the changes.

The changes may be too subtle or they may lack fertile quality cervical mucus. This can occur naturally because of aging, or it can be the side effect of some medications. (Clomid, for example, in high doses can dry up cervical discharge.)

Having little to no cervical mucus can also be a side of a hormonal imbalance or risk factor for infertility.

Some women get fertile quality mucus for days and days, making it an impractical method of timing sex for conception. This is true for women with polycystic ovarian syndrome.

Your cervix also changes as ovulation approaches. Some women track these cervical changes on a fertility chart.

Using an Ovulation Predictor Test to Detect Ovulation Day

An ovulation predictor kit can help determine your ovulation day.

Ovulation predictor kits work like pregnancy tests, in that you pee on a stick or strip of paper. But unlike pregnancy tests, you don’t take just one to detect ovulation. You will actually need to use several over a period of days.

On an ovulation predictor test, you’ll also get two lines. When the test line is darker than the control line, ovulation day should occur within the next 48 hours.

(If you’re using a digital test, you won’t need to evaluate lines: The test should just tell you if you’re ovulating or not.)

Sounds simple! Except, it isn’t always.

If you have irregular cycles, ovulation tests can become expensive. You’ll need to take them over many more days than someone with regular cycles. The costs can add up.

Also, they aren’t effective in all women. Just like with the cervical mucus, women with polycystic ovarian syndrome may get positive ovulation test results on several days. Those results may not indicate ovulation.

(This occurs because of multiple surges of the hormone LH. LH is what triggers the egg in the ovaries to go through the last stages of maturity and finally ovulate. In women with PCOS, it may fail to trigger ovulation. This leads to several LH surges.)

All that said, some women have great success with ovulation test kits.

Body Basal Temperature Charting and Ovulation Day

Your body basal temperature (BBT) is your body's temperature at rest. If you take your temperature first thing in the morning, before you get up or brush your teeth, you'll get your basal temperature.

Progesterone is a hormone that rises after ovulation. This hormone also causes your body’s basal temperature to rise.

By charting your BBT, you can figure out your ovulation day. After three consecutive days of raised body temperature, you can assume that ovulation occurred on the day before or of the first temperature rise. Sometimes, women will see a slight dip in body temperature the day of ovulation, followed by the three higher temperatures.

There are free BBT charting computer programs and websites, so don't worry—graphing know-how isn't necessary!

The disadvantage of using your BBT to detect ovulation is you'll only know after it passes, about three days past your ovulation day. You can really use charting to predict ovulation day, unless you’re looking for a pattern month to month.

If your cycles are somewhat regular, a BBT chart can help you estimate future ovulation days. If your cycles are irregular, you may not be able to estimate from month to month.

Other Ovulation Signs and Symptoms

While you may not have noticed before, ovulation day is proceeded by a number of signs and symptoms.

Increasing fertile cervical mucus is one, but there are others, including an increased desire for sex and ovulation pains.

If you're aware of ovulation signs and symptoms, you may be able to figure out intuitively that ovulation day is coming.

Of course, intuition is probably not going to give you an exact day. But you don’t really need to know the exact day.

You just need to know when you’re approaching ovulation. It’s the days before you ovulate that you are most fertile.

Do You Really Need to Know Your Exact Day of Ovulation?

Here’s the bottom line: It doesn’t really matter if you know your exact ovulation date.

In fact, research has found that it may not be possible for you to even know your exact ovulation day.

Studies comparing ultrasound results to basal body temperature chart results found that charting predicted ovulation day correctly only 43 percent of the time. Ovulation predictor kits, which detect the LH hormone surge, may be accurate only 60 percent of the time.

All of this is actually good news... it means you don’t need to stress out over having sex on the day before ovulation.

As long as you have sexual intercourse when there are possible fertile signs, or have sex frequently all month long, your odds of conceiving are good.


Bigelow JL, Dunson DB, Stanford JB, Ecochard R, Gnoth C, Colombo B. Mucus Observations in the Fertile Window: A Better Predictor of Conception Than Timing of Intercourse. Human Reproduction. 2004; 19(4):889-92. Epub 2004 Feb 27.

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