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How to Chart Basal Body Temperature

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Tracy is a nurse and works in a local hospital, specializing in traditional care. She especially loves making a difference in people' lives.

Basal Body Charts: How to Track Your Ovulation

Basal Body Charts: How to Track Your Ovulation

Basal body temperature charting (BBT charting) is used by many women to help track and understand their monthly cycles. This technique is used for both trying to conceive and trying to prevent pregnancy. It is easy and can be performed in the comfort of your own home.

Why Should You Chart Your Basal Body Temperature?

Charting can help you. . .

  • pinpoint ovulation (not everyone ovulates on day 14 of their cycle).
  • find your "fertile window" and increase or decrease your chances of becoming pregnant.
  • discover whether or not you are actually ovulating.
  • avoid any unwanted pregnancies by knowing and avoiding sexual intercourse during your fertile period.
  • determine whether there are any problems with your monthly cycle, such as anovulation (not ovulating), luteal phase problems, etc.

How to Chart Your Basal Body Temperature (BBT)

When creating your BBT chart, you may do it the old-fashioned way with pen and paper (like in the pictures I have provided) or, if you prefer to use technology, there are many apps and websites that you can use. Below, we'll cover

  • how and when to take your temperature,
  • how to set up and add data to your chart, and
  • terms you'll need to know in order to interpret the results.

How Do I Take My Basal Body Temperature?

For best results, purchase a basal body temperature thermometer. These are usually digital and will read your temperature up to one-tenth or one-hundredth of a degree. You need a thermometer that will at least read to a tenth of a degree, as the body's temperature may change less than one whole degree each day.

Can I use a regular thermometer?

Yes, you can use a regular thermometer to chart your basal body temperature, but it might be slightly less precise. These thermometers are not as accurate, but many women have had no problems using them to determine ovulation.

How do I take my temperature?

Choose a route in which you are going to check your temperature: orally, vaginally, or rectally. It does not really matter which you choose, as long as you take it the same way every time. Do not switch from taking the temperature vaginally to orally, for example: if you choose to check your temperature orally, check it orally every time.

When should I take my temperature?

Basal body temperature is the coolest temperature your body drops to while at rest, so only check your basal body temperature after you have had at least four hours of sleep.

Take your temperature before you get out of bed for the most accurate result. It is best to take your temperature at the same time every day. Set an alarm if you need to. For every additional hour you sleep in, it is said that your body temperature raises slightly, so taking it at the same time every day will give you the most accurate result.

What if I am late taking my temperature?

If you are not able to take it at exactly the same time every day, your results should still give you a fairly accurate ovulation reading.

Still, try to take it before you get up, because once your body is moving or if you eat, drink, or smoke, your temperature will change, and the basal body temperature will not be as accurate. So keep a thermometer within arm's reach of your bed.

What factors might affect my temperature?

There are a few factors that may give you inaccurate results, including

  • illness
  • an environment that is too cold or too warm
  • taking your temperature at different times of the day
  • eating or drinking before taking your temperature
  • smoking before taking your temperature
  • making too much movement before taking your temperature
  • mouth breathing while sleeping

Sample Homemade Basal Body Temperature (BBT) Chart

Sample Homemade Basal Body Temperature (BBT) Chart

Sample Homemade Basal Body Temperature (BBT) Chart

How Do I Chart My Basal Body Temperature?

You can make a paper chart, use a program on your computer, or use an app on your cellphone or another device. Take your temperature consistently every morning and do not forget to chart it. Do this every day until menstruation begins. Menstruation is the first day of a new cycle, and a new cycle requires a new chart.

How Do I Know If or When I Ovulated?

Ovulation is often determined by the "three-over-six rule": If you see a three-day upward trend in temperature after at least six days of lower readings, this may indicate ovulation. After you see three consecutive days of heightened temperature (.5 Fahrenheit or 0.3 Celsius degrees or more), that is your sign that ovulation has likely occurred.

For example, see this account of cycle days (CD):

Six recorded days of lower temperatures: CD#11: 97.2, CD#12: 97.4, CD#13: 97.3, CD#14: 97.3, CD#15: 97.4, CD#16: 97.4

Three recorded days with a temperature gain: CD#17: 98.2, CD#18: 98.1, CD#19: 98.3

Three days of an upward temperature shift of at least 0.4 degrees indicates the likelihood of ovulation.

On which day did I ovulate?

In this example, ovulation likely happened on cycle day 16 (CD#16), as it was the last day of the low temperatures. The upward shift of 0.8 degrees (more than 0.4) remaining high for three consecutive days is the clue that the egg was released.

The Phases of an Average 28-Day Menstrual Cycle

Menstruation (Menses Day 1-7)

Menstruation is the loss of blood and tissue through the vagina from the uterus. Every month, the uterus lining thickens to prepare for pregnancy. If there is no fertilized egg, then progesterone levels will drop and the uterine lining will begin to shed, marking the first day of the menstrual cycle.

The Follicular Phase (Day 1-14)

The follicular phase of the menstrual cycle is the first half of the cycle. A woman's basal body temperature is generally lower during this half compared to the second half (the luteal phase; see below). The follicular phase begins on the first day of your period and ends the day you ovulate. When the luteinizing hormone is at its highest point, the ovaries are signaled to release the egg into the fallopian tubes, therefore ending the follicular phase and beginning the luteal phase. It is at the end of this phase that the woman is most fertile.

Ovulation (10 to 16 Days Before/After Your Period)

You may be able to predict when the egg is released if you have a regular cycle.

The Luteal Phase (Day 14-28)

The luteal phase—the second half of the menstrual cycle—is the stretch that begins the day after ovulation and ends the day before menstruation begins. The average luteal phase is 14 days long and must be at least 10 days long to support a pregnancy. A luteal phase shorter than ten days is called a "luteal phase defect." During the luteal phase, a woman's temperature will be slightly higher (0.4 degrees Fahrenheit or more) than it was during the follicular phase. This is due to the corpus luteum producing the hormone progesterone.

Do the Luteal and Follicular Phases Remain Constant?

The length of your cycle may vary from month to month. However, the luteal phase usually remains fairly consistent. It is the follicular phase that changes, lengthening and shortening your cycle.

Sample Homemade Follicular Phase of BBT Chart

15 days of the follicular phase; ovulation on cycle day 16.

15 days of the follicular phase; ovulation on cycle day 16.

Sample Homemade Luteal Phase on BBT Chart

Note: Not everyone experiences an ovulation dip (dip in temperature the day of ovulation).  Luteal phase shown with temperature jump of 0.8 degrees between follicular and luteal phase.

Note: Not everyone experiences an ovulation dip (dip in temperature the day of ovulation). Luteal phase shown with temperature jump of 0.8 degrees between follicular and luteal phase.

FAQ and Terms to Know

Basal Body Temperature

Basal body temperature is the body's lowest temperature at rest. For accuracy, it is best to take your temperature before getting out of bed. Moving, eating, drinking, or smoking can affect your temperature.

Sample BBT Chart Showing 6 Days Under and 3 Days Over

This image shows how to determine when ovulation occurred using the 6 days under the cover line and the 3 days over the coverline rule.

This image shows how to determine when ovulation occurred using the 6 days under the cover line and the 3 days over the coverline rule.

Coverline

The "coverline" is a horizontal line on your BBT chart that marks the shift from average pre-ovulation temperatures (cooler) to average post-ovulation temperatures (warmer). It is in the luteal phase and marks the time between ovulation and your expected period. The coverline helps you visualize the pattern of your thermal shift.

BBT Chart Showing Coverline

This photo shows how a coverline works. The coverline is drawn 0.1 degree above your highest follicular phase temperature.

This photo shows how a coverline works. The coverline is drawn 0.1 degree above your highest follicular phase temperature.

Cycle Day (CD)

Cycle day (CD) is what day of your cycle you are on. This may go from CD#1 to CD#28 or more, depending on how many days there are during your cycle before menstruation begins again. The term "cycle day" continues even after ovulation has occurred.

Days Past Ovulation (DPO)

Days past ovulation (or DPO) begin the day after ovulation has occurred. Day 1 of DPO is the day after ovulation. Most women should expect menstruation to begin on Day 15 DPO (on average), but it commonly happens from day 11 to day 16 DPO. If a woman makes it to 18 DPO but there has been no menstruation and her temperatures have remained high, there is a high probability of pregnancy.

Sample Homemade BBT Chart Showing DPO

This image shows how days past ovulation works. It continues until menstruation starts.

This image shows how days past ovulation works. It continues until menstruation starts.

Fallback Rise

A fallback rise usually occurs 2 DPO (days past ovulation). Ovulation occurs, the basal body temperature rises the next day, and then it falls again to or below the coverline the next. After this "fallback", the basal body temperature will once again rise at least 0.4 degrees above the cover line.

Implantation Dip

Not everyone will experience an implantation dip, which is when temperatures dip below coverline around the time of implantation (around 7-10 DPO). Although this dip happens more commonly in pregnant cycles, it does not necessarily mean that you are pregnant. Some women sometimes experience this dip in temperature even when they are not pregnant.

Sample Homemade BBT Chart Showing Implantation Dip

Note: This picture is showing an implantation dip. Not everyone experiences and implantation dip.

Note: This picture is showing an implantation dip. Not everyone experiences and implantation dip.

Luteal Phase Defects

A luteal phase defect is when the uterine lining does not become thick enough to sustain a pregnancy. This may happen because insufficient progesterone is produced or the lining of your uterus is not using the progesterone properly. This may cause your periods to start earlier than expected (a short luteal phase), spotting between your periods, and/or difficulty getting pregnant. It is best to speak to your healthcare provider if you suspect you are experiencing a luteal phase defect.

Ovulation Dip

Not all women experience an ovulation dip. However some do, and being able to identify it will help them to recognize when ovulation has occurred. An ovulation dip is when the basal body temperature drops lower than usual on the day of ovulation, then raises above the coverline and remains there, indicating that ovulation may have occurred.

Sample Homemade BBT Chart Showing the End of Cycle

This BBT chart shows the cycle ending. Cycle day (CD) 30 or 14 days past ovulation (dpo) is the last day of the previous cycle. A temperature drop and the start of menstruation indicate the beginning of a new cycle.

This BBT chart shows the cycle ending. Cycle day (CD) 30 or 14 days past ovulation (dpo) is the last day of the previous cycle. A temperature drop and the start of menstruation indicate the beginning of a new cycle.

Frequently Asked Questions About Ovulation and Basal Temperatures

Here is a list of facts regarding your basal body temperature (and charting):

  • Ovulation does not always occur on day 14 of your cycle. Day 14 is only an average. You may ovulate sooner or later (day 12 or day 20 for example).
  • To determine whether or not ovulation has occurred, use the 3 over 6 rule: Three consecutive higher temperatures following 6 lower temperatures.
  • There is a good chance of pregnancy if your temperature remains high and you have not yet gotten your period by 18 DPO (days past ovulation).
  • Once you choose a method of checking your temperature (orally, vaginally, or rectally), you must remain consistent throughout your cycle and use that same method every time.
  • Not everyone has a 28-day cycle. Twenty-eight days is only an average (some may be 26 days or 40 days, for example, and some fluctuate).
  • Not all luteal phases are 14 days.
  • You must have at least a 10-day luteal phase to sustain a pregnancy.
  • The follicular phase is the first half of your cycle when your temperatures are generally lower.
  • The luteal phase is the second half of your cycle when your temperatures are generally higher, occurring after ovulation.
  • Take your temperature at the same time every day.
  • Eating, smoking, and/or drinking can alter your basal body temperature.
  • BBT charting will only tell you if/when you have ovulated, not when you are about to ovulate.

Pregnant BBT Chart

Temperature did not drop for 18 days past ovulation and menstruation did not show up. This is likely a pregnant cycle.

Temperature did not drop for 18 days past ovulation and menstruation did not show up. This is likely a pregnant cycle.

There's an App for That!

Here is a list of some apps for your phone or another device that you can use to easily track your menstrual cycle.

For Android

  • Basal Body Temperature
  • Menstrual Calendar
  • Fertility Friend App
  • My Fertility Charts

For Apple

  • Kindara Fertility Tracker
  • BBT
  • BodyTemp and Period Monitor
  • Period View

This content is accurate and true to the best of the author’s knowledge and does not substitute for diagnosis, prognosis, treatment, prescription, and/or dietary advice from a licensed health professional. Drugs, supplements, and natural remedies may have dangerous side effects. If pregnant or nursing, consult with a qualified provider on an individual basis. Seek immediate help if you are experiencing a medical emergency.

Comments

Mrs joy on December 18, 2019:

My last period was 27th of last month when is my ovulation

oge on July 24, 2019:

try to conceive

Kelly on November 15, 2018:

I have 3 girls. I need a baby boy. Please help me

Ivanildo on January 14, 2015:

Temps should be taken at the same time every day, so even on the wekednes I set my alarm for 5am to temp, then I go back to sleep. Luckily my thermometer stores the last temperature so I don't have to worry about entering it until I'm awake.Oral temperatures didn't work for me because I sleep with my mouth open and I snore. I found that two temps would be drastically different even if I took one right after the other.TMI: I prefer vaginal temping because I can hit snooze, insert the thermometer and then take it out when the alarm goes off again. Before I fell asleep with the thermometer in my mouth multiple times. It's only slightly more inconvenient because I have to keep a pack of antibac wipes in my nightstand to wipe it down every morning, otherwise it grosses me out.

Julia on January 13, 2015:

Hi Jenna!You might want to get a hormone pnneal run. If you do the blood test a couple days before you expect your period you can also validate if you ovulated. Looking at your charts there isn't clear signs of ovulation. The dotted line on FF indicates that there are some inconstancies between your temps and other fertility signs so you might be right.I know some doctors want to "wait" before running any tests but it doesn't make any sense to me. Your charts indicate irregularities and a hormone panel is a simple test to run. My Naturopathic Doctor ran thyroid, LH (should indicate if you ovulated), Progesterone, Estrogen, and a couple others I can't remember. I actually sought out my ND for TTC because I knew my PC physician wouldn't be very proactive and I didn't really want to get an OB/GYN unless I had to (I plan to use midwife during pregnancy and geeee just my luck my ND is also a midwife!). Hopefully your Dr will be open to running some basic tests.

Margery on January 10, 2015:

That saves me. Thanks for being so sesbnile!