Basal Body Temperature (BBT): How to Track Ovulation (2023)

Understanding the hormonal cycles of the female reproductive system and how they affect your body can be helpful when trying to become pregnant or avoid pregnancy. Hormones play a big role by helping the brain, ovaries, and uterus communicate. Basal body temperature (BBT) is one outward sign to predict when your body is most fertile.

This article discusses the basics of the female menstrual cycle, the fertile window, and how checking BBT can provide useful information for women trying to conceive or avoid pregnancy.

The words “female” and "woman" are used throughout this article to refer to people who identify as female and have typical reproductive organs of a cisgender female. We recognize that some people who identify as female do not have the same anatomy as that depicted in this article.

Basal Body Temperature (BBT): How to Track Ovulation (1)

Basics of the Female Reproductive System and Fertility

Each month, hormones cause changes in the ovaries and uterus to prepare the body for potential pregnancy. The cycle begins with menstruation, the phase when the uterus sheds its lining.

On the first day of menstruation, the ovaries are busy responding to a hormone released from the brain, called follicle-stimulating hormone (FSH). FSH tells the ovaries to make immature eggs, called follicles. These follicles secrete the hormone estrogen, which has effects throughout the body.

When estrogen rises to a certain level, it signals the brain to release luteinizing hormone (LH), which then triggers ovulation.

During ovulation the mature egg is released from the most dominant follicle and travels through the fallopian tubes to the uterus. The leftover follicle becomes a hormone-secreting cluster of cells called the corpus luteum, meaning “yellow body” in Latin.

The corpus luteum secretes several hormones, including progesterone. Progesterone causes the uterine lining to thicken in preparation for accepting a fertilized egg. Progesterone also causes changes in cervical secretions that promote sperm motility.

If fertilization does not occur, the corpus luteum breaks down and the subsequent decreased levels of progesterone and estrogen cause menstruation. If fertilization occurs, human chorionic gonadotropin (hCG), secreted by the embryo, causes the corpus luteum to remain and keep secreting hormones. The ongoing progesterone secretion maintains the uterine lining for pregnancy.

The Fertile Window

The fertile window is the period in which sexual intercourse can result in pregnancy. After ovulation, the egg can live for up to 24 hours. Sperm can live in the female reproductive tract for up to five days.

Having sexual intercourse in the two days leading up to ovulation has the highest chance of resulting in pregnancy, but you can become pregnant any time in the five days before ovulation and the day of ovulation.

Basal Body Temperature (BBT): How to Track Ovulation (2)

What Is Basal Body Temperature?

BBT is the body’s temperature when in a state of rest. In general, the body’s resting temperature is stable from day to day. In women, predictable changes in body temperature occur at specific points in the menstrual cycle.

During the first half of the menstrual cycle, from menstruation until ovulation, the temperature is relatively low. Once ovulation occurs and progesterone levels rise, the body temperature increases by up to 0.5 degrees. The temperature remains relatively high until progesterone levels drop and menses occurs.


This information can be useful for people trying to conceive and for those trying to avoid pregnancy. Women trying to conceive can use BBT to predict ovulation in order to time intercourse during the fertility window.

BBT is also a method used in natural family planning for women who want to use abstinence or barrier contraception methods during the fertile window to decrease the chances of becoming pregnant.

How to Take Basal Body Temperature

After ovulation, the rise in progesterone levels in the luteal phase causes an increase in basal body temperature of 0.5–1 degree. If fertilization does not occur, the fall in progesterone causes the temperature to again drop to the lower level.

The changes in basal body temperature may be as small as 0.5 degrees, so it's important to use a thermometer with accuracy to within 0.1 degrees. Anything less accurate can miss the small changes needed for fertility prediction.

Some thermometers are designed specifically for BBT that may provide some added value.

Risks of BBT

  • Not accurate in women who have irregular menstrual cycles

  • Increase in temperature occurs during or after the fertile period, so the fertile period could be missed

  • BBT method alone is a less effective method for preventing pregnancy than other forms of birth control

Benefits of BBT

  • Inexpensive

  • No side effects

  • Does not involve risks of hormonal contraception

Normal Basal Body Temperature

Normal body temperature varies from person to person, but it generally ranges from 96 to 99 degrees F. Temperature varies slightly depending on how it is measured, and it can change during certain times of the day and with activity, stress, changes in sleep patterns, or illness.

How to Chart Temperature Changes

Since the increase in BBT occurs at or after ovulation, the fertile period begins several days before you notice a drop in temperature. In other words, you can become pregnant in the week leading up to an increase in temperature. However, charting your temperature over time can provide information about the timing of your cycle to predict fertility in future months.

When measuring BBT, the body should be completely at rest. Keep a thermometer within reach at your bedside so you can take your temperature immediately upon waking, before getting out of bed, or doing any activity.

Temperature should be taken at approximately the same time each day and using the same thermometer in the same location. Taking your temperature by mouth is the most common way to measure basal body temperature, but vaginal and rectal temperatures may also be used.

(Video) How to Measure Basal Body Temperature | Pregnancy Questions | Parents

After charting basal body temperature for a few months, you will notice a pattern of lower temperatures for a couple of weeks, followed by a slight rise in temperature that plateaus and remains until menstruation. Use this information to predict the timing of ovulation and your fertile window in future months.

Tools to Track BBT

Other than a thermometer, all you need is a pen and paper to plot your temperature on a graph or table each day. Also, several phone apps have been designed specifically to plot BBT and provide insight into your cycle and fertile window.

Other Signs of Ovulation

BBT is one of several signs you can use to track your fertile window.

Hormones cause several other changes in the body. A combination of fertility awareness methods can be used for those trying to conceive to time intercourse, or they may be combined with barrier contraception or abstinence during the fertile period to avoid pregnancy. Methods include:

  • Calendar method: Many women have a predictable menstrual cycle length that can be used to predict the fertile window. The average cycle is 28 days, and ovulation typically occurs midway through the cycle, around day 14. This information can be used to estimate when the fertile window is to time intercourse and increase or decrease chances of pregnancy.
  • Cervical mucus method: Cervical mucus changes predictably during the menstrual cycle. During the most fertile period, cervical secretions are clear and stretchy to assist sperm motility.
  • Mittelschmerz: Mid-cycle pain and cramping that some women experience during ovulation can help predict when it's occurring.
  • Hormone measurement: LH can be measured at home using urine tests. A rise in LH (LH surge) triggers ovulation, so timing intercourse at this time can increase chances of pregnancy in women trying to conceive.

Basal Body Temperature When Pregnant

The hormone changes that occur with pregnancy also affect BBT. A couple of findings on the BBT chart can be early signs of pregnancy. Of course, suspected pregnancy should be confirmed with a pregnancy test and a visit to your healthcare provider.

One very early potential sign of pregnancy is a one-day drop in temperature, called the implantation dip. This can occur about a week after ovulation if fertilization has occurred and lasts for just one day. Compare this to a typical cycle when a dip will be seen just before the onset of your period and will remain low until the next time you ovulate.

An implantation dip is not the most reliable sign of pregnancy because it may not be present. If it's present, it does not always mean pregnancy.

A more predictable and noticeable change in BBT that can indicate pregnancy is a prolonged increase in temperature. During pregnancy, progesterone levels remain high and cause a sustained increase in BBT.

Look for other pregnancy signs, like a missed period and symptoms like fatigue and nausea.


Basal body temperature is a noninvasive, inexpensive, and simple measure that can be used to track fertile periods for those trying to conceive or avoid pregnancy. BBT relies on charting daily temperature and noticing small changes over time to predict future fertility windows.

A Word From Verywell

Trying to get pregnant or avoid pregnancy using hormone-free methods can be challenging. While the BBT method can be helpful for tracking your cycle and fertile window, your body temperature can be affected by many external factors and relies on tracking very small changes over time.

Not all women will be able to reliably predict ovulation, particularly if they have irregular menstrual cycles. Speak with your healthcare provider with any concerns you have about infertility or choosing the right form of birth control.

Frequently Asked Questions

  • What is the basal body temperature during your period?

    Basal body temperature drops when your period starts because of the decline in progesterone levels. If basal body temperature remains elevated and you miss your period or only have light spotting, take a pregnancy test.

  • How long is your fertile window each month?

    The fertile window is based on how long sperm and a released egg can survive in the female reproductive tract. Sperm can survive for up to five days. A released egg can survive for up to 24 hours after ovulation. Adding these together give you a fertile window of approximately six days.

    (Video) How To Get Pregnant - Record Your Basal Body Temperature (BBT) - Series 1 - Episode 4
  • Can you tell if you are pregnant through just your basal body temperature?

    A persistent increase in basal body temperature can indicate pregnancy due to higher progesterone levels, but this should not be the only sign you rely on. It will coincide with a missed period (or very light spotting from implantation bleeding). Always confirm suspected pregnancy with a pregnancy test.

3 Sources

Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.

Basal Body Temperature (BBT): How to Track Ovulation (3)

(Video) Why don't my basal body temperature chart patterns match the my ovulation predictor kit results?

By Angela Ryan Lee, MD
Angela Ryan Lee, MD, is board-certified in cardiovascular diseases and internal medicine. She is a fellow of the American College of Cardiology and holds board certifications from the American Society of Nuclear Cardiology and the National Board of Echocardiography. She completed undergraduate studies at the University of Virginia with a B.S. in Biology, medical school at Jefferson Medical College, and internal medicine residency and cardiovascular diseases fellowship at the George Washington University Hospital. Her professional interests include preventive cardiology, medical journalism, and health policy.

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How reliable is BBT for confirming ovulation? ›

While BBT rises during the second half of your menstrual cycle after ovulation occurs (called the luteal phase), it's a better predictor of whether you've already ovulated. Overall, it's an unreliable way to get a read on your ovulation patterns due to how many factors influence your body's temperature.

How do you measure basal body temperature? ›

To use the basal body temperature method:
  1. Make sure you have a thermometer that measures temperatures to at least one-tenth of a degree. ...
  2. Take your basal temperature at the same time every day. ...
  3. Measure the temperature from the same place every day. ...
  4. Record the temperature each day. ...
  5. Identify a temperature increase.
23 Apr 2019

How many days after ovulation does BBT rise? ›

It can take up to three days after ovulation for the temperature to rise. However, in our experience most women experience temperature rises on the same day or a day later than when an ovulation predictor kit turns positive.

How do you confirm ovulation? ›

There are several ways to detect ovulation, including urine test kits to measure LH levels, transvaginal ultrasound, endometrial biopsy, blood tests to measure hormone levels, and the basal body temperature (BBT) chart.

What is the most accurate way to track ovulation? ›

Ovulation predictor kits are considered one of the most accurate methods of predicting ovulation. Similar to home pregnancy urine tests, ovulation test strips measure your luteinizing hormone (LH) levels and show a particular color when these levels surge.

How long after ovulation pain is the egg released? ›

The release of the egg from the follicle and ovary happens about 24 hours later (10–12 hours after LH peaks) (13, 17).

Can you ovulate without a rise in BBT? ›

Contrary to popular belief, basal body temperature doesn't always rise immediately after you ovulate. According to a study that compared BBT readings with ultrasound—the gold standard in confirming ovulation—only 11 percent of women have a basal body temperature rise within one day of ovulation.

Does BBT rise if you don't ovulate? ›

Women who ovulate and check their basal body temperature (BBT) chart will probably notice a small, but sustained rise in temperature after ovulation, especially after a few months of experience with close monitoring. A woman who is not ovulating will not have that small temperature change.

Why is my BBT so low after ovulation? ›

The Connection Between Temperature & Progesterone

During the follicular phase, which begins on the first day of your period and ends when you ovulate, most women experience naturally low progesterone levels — resulting in generally lower temperature readings.

How long do you ovulate for? ›

While ovulation itself only lasts for 12 to 24 hours, you're most likely to get pregnant in the days before and after ovulation, a window of around six days. Read on to learn more about what exactly happens during this phase of the menstrual cycle, as well as reasons why ovulation can be delayed.

Where is the best place to take your basal body temperature? ›

Put the thermometer in your mouth to take the reading.

You can take your basal body temperature by putting it in your mouth in the same location every morning. Keep it in your mouth for several seconds to allow the thermometer to get an accurate reading.

What does BBT look like if pregnant? ›

Seeing a triphasic pattern on your BBT chart is slightly more likely to indicate a potential pregnancy, but it is also no guarantee. A triphasic pattern indicates that progesterone rose a little bit more, causing your temperatures to also rise slightly more. This may occur because you're pregnant.

Can you take your basal body temp with a regular thermometer? ›

The change in your body temperature is very slight, so you need to use a special thermometer to measure it. You can use a regular digital thermometer, or you can buy a basal thermometer. A basal thermometer shows you the temperature in tenths of a degree. This allows you to note tiny changes in body heat.

How do I know my ovary released an egg? ›

Common Signs of Ovulation
  1. Positive Ovulation Test Result.
  2. Fertile Cervical Mucus.
  3. Increased Sexual Desire.
  4. Basal Body Temperature Increase.
  5. Change in Cervical Position.
  6. Breast Tenderness.
  7. Saliva Ferning Pattern.
  8. Ovulation Pain.
17 Oct 2022

How do you release two eggs during ovulation? ›

How is it performed? Women who naturally ovulate may release extra eggs when they take oral medications such as clomiphene. This is a mild form of superovulation and is generally low in cost and risk.

How do you know if you have a fertilized egg discharge? ›

Cervical mucus changes can be an early sign of pregnancy. After implantation (when a fertilized egg attaches to your uterus), mucus tends to be clear, thick, and gummy. Some people experience implantation bleeding, or spotting, which can occur 6 to 12 days after conception.

Does a faint line on an ovulation test mean I will ovulate soon? ›

If the test line shows up darker than the control line, you're about to ovulate. (There are always low levels of LH in your body, so if the test line shows up but appears lighter or fainter than the control line, you're not ovulating yet.

At what day is the egg released? ›

In an average 28-day menstrual cycle, ovulation typically occurs about 14 days before the start of the next menstrual period.

How do you manually track ovulation? ›

Basal body temperature charting (BBT charting) involves taking your temperature first thing in the morning, before you even rise from bed. A sustained temperature increase indicates that you have ovulated. By maintaining a chart over the duration of your cycle, you can detect these temperature changes.

What is your temperature when you are ovulating? ›

Your body temperature dips a bit just before your ovary releases an egg. Then, 24 hours after the egg's release, your temperature rises and stays up for several days. Before ovulation, a woman's BBT averages between 97°F (36.1°C) and 97.5°F (36.4°C). After ovulation, it rises to 97.6°F (36.4°C) to 98.6°F (37°C).

Where do you put a basal thermometer? ›

You can measure your basal body temperature orally, vaginally, or rectally. Measurement of the temperature vaginally or rectally provides higher temperatures than measuring orally. It is important that you always measure in the same way and the same place.

Can you use a regular thermometer for BBT? ›

You can use a regular digital thermometer or buy a basal thermometer. A basal thermometer shows you the temperature in tenths of a degree. This allows you to note tiny changes in body heat.

Do I need a special thermometer for BBT? ›

Women can document their BBT with just a simple mercury thermometer and a piece of paper; Dr. Twogood says “You don't need anything fancy! I find that technology helps some people but confuses other people.” However, Dr.

What time of day does ovulation occur? ›

LH typically rises in the morning, between 4–8 am (29). If you test before it first rises, you may get a negative result that day, but you should still get a positive result the next day.

How long do you ovulate for? ›

While ovulation itself only lasts for 12 to 24 hours, you're most likely to get pregnant in the days before and after ovulation, a window of around six days. Read on to learn more about what exactly happens during this phase of the menstrual cycle, as well as reasons why ovulation can be delayed.

Which day egg is released in ovary? ›

In an average 28-day menstrual cycle, ovulation typically occurs about 14 days before the start of the next menstrual period.

What if temp doesn't rise after ovulation? ›

May Not Be Ovulating

If you have fertile cervical mucus but no rise in temperature, it could be that you're not ovulating. 1 While fertile quality cervical mucus can warn you that ovulation is coming, so you can time sex for pregnancy, it doesn't confirm that ovulation actually took place.

How does ovulation look like? ›

As ovulation nears, your discharge will become wet, stretchy and slippery. The most common analogy used for super fertile cervical mucus is looking and feeling like raw egg whites. If you see that texture, you will know you're at your most fertile time.

What is the difference between basal body temperature and regular temperature? ›

Basal body temperature is the temperature of the body at a resting period. It is the lowest temperature of the body. Regular temperature is the average body temperature of a healthy individual at any time. Thus, this is the key difference between basal body temperature and regular temperature.

Can you get pregnant on day of temperature rise? ›

Because basal body temperature only rises after ovulation has taken place, you want to have intercourse before your temperature rise and maybe even include the day of your temperature rise. To further increase your chances of getting pregnant, tracking your cervical mucus comes into play.

Do basal thermometers really work? ›

It's not a reliable method of birth control, though: About 24 in 100 women who use fertility-awareness-based methods like BBT to prevent pregnancy will still get pregnant over 12 months of use.


1. How to chart your basal body temperature / BBT
(Fertility Friend)
2. Basal Body Temperature Tracking Do's & Don'ts
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3. How to Track your Cycle to Get Pregnant! BBT Charting and Ovulation Tracking Explained.
(Sophie Pickles)
4. Trying to Conceive: Tracking Basal Body Temperature to Get Pregnant Fast | Parents
5. Using Basal Body Temperature (BBT) to Track Ovulation
(Dr. Shannon Vander Doelen ND)
(Bright Girl Health)
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