How to chart basal body temperature to predict ovulation

What is basal body temperature?

Your body’s temperature at rest is your basal body temperature or BBT. This is your lowest temperature in a day (24 hours). Usually, the basal body temperature increases and stays raised after ovulation.

If your menstrual cycles are regular, you can track your basal body temperature over time to predict: 

• When you’ll ovulate

• What your most fertile days would be

To increase the accuracy of predicting ovulation, you can monitor your basal body temperature along with tracking your cervical mucus and using our Ovulation Calculator.

In case of any fertility issues, charting your basal body temperature can also help your Doctor determine the underlying cause.

Read on to find out how tracking your basal body temperature can help detect and predict ovulation.

How to take basal body temperature

To measure your basal body temperature accurately, you need to do the following:

• Use a basal thermometer that is specially designed for measuring the slightest changes in your body temperature

• Take a reading right after waking up, before you get out of bed or do anything, otherwise your basal body temperature tracking would not be accurate

• Try to take your temperature around the same time every morning

• Record your basal body temperature in an ovulation chart (see the sections below)

You can also use our Ovulation Calculator along with the basal body temperature method to track ovulation.

Can you use a regular thermometer to take basal body temperature?

To accurately track your basal body temperature, you need to use a basal body thermometer that can detect the smallest of changes in your body temperature. You can use either a digital or a glass basal body thermometer as long as it can measure the temperature to one-tenth of a degree.

What is normal basal body temperature?

The following are considered normal basal body temperatures depending on where you are in the menstrual cycle:

• Before ovulation: 97.2-97.7 °F

• Just after ovulation: An increase of 0.5-1.0 °F that usually lasts till the start of your next period 

Your basal body temperature could also spike on other days, but you’ve most likely not ovulated if the temperature drops instead of staying raised.

Other factors that can raise your basal body temperature are as follows:

• Pregnancy 

• Fever

• Medications, such as blood pressure pills and antibiotics

• Diseases, such as thyroid disorders 

• Hot weather 

• Exercise or exertion

What is cervical fluid?

Cervical mucus or fluid is a vaginal discharge secreted by the cervix. Changes in cervical mucus correspond with hormonal fluctuations throughout the menstrual cycle. As the hormone levels change, you may notice a change in the following aspects of your cervical mucus:

• Amount

• Color

• Consistency or texture 

You may experience little to no discharge after your period ends. However, during ovulation and in the days leading up to it, your cervical mucus may become:

• Thin and clear

• Slippery and stretchy (like egg whites)

By monitoring your cervical mucus, you can tell when you're most likely to ovulate and what your most fertile days could be. 

Learn more about cervical mucus.

Basal body temperature and cervical mucus charts to track ovulation

Here’s a sample chart that you can use to track your basal body temperature and cervical mucus changes daily: 

After charting your basal body temperature and cervical mucus for a few menstrual cycles, you’ll be able to recognize patterns that could indicate when you’re going to ovulate next. 

Since the menstrual cycle could vary from woman to woman and from month to month, your personal ovulation charts may differ from month to month as well.

You can also use our free Ovulation Calculator to easily predict your most fertile days.

How to use basal body temperature and cervical mucus charts to predict ovulation

To track your basal body temperature and cervical mucus, do the following:

1. In an ovulation chart, note the first day of your period as Day 1 of your cycle. In this chart, you’ll need to record the dates and temperatures for the current menstrual cycle, i.e., until the first day of your next period.

2. Use a basal body temperature thermometer to take your temperature the first thing in the morning. Record your temperature every day as soon as you wake up, before you have anything to drink or eat, or even sit up in bed. 

3. Put down a dot against the corresponding temperature in the chart. 

4. Check your cervical mucus daily as well. Learn about the ways to check cervical mucus. 

5. Record the type of cervical mucus you see each day. Follow the key at the chart bottom, i.e.: 

   1. P = Period

   2. D = Dry

   3. S = Sticky

   4. E = Egg white-like

6. At the end of the cycle, connect the dots on the chart to see how your temperature rises and drops throughout the cycle and what those changes mean: 

   1. Ovulation has usually occurred when your basal body temperature increases by 0.5-1 °F and stays raised

   2. On the ovulation day and the days leading up to ovulation, your cervical mucus becomes egg white-like as well

   3. The 2-3 days before the increase in your basal body temperature is your most fertile period

7. Track your temperature and discharge for a few months to see if your basal body temperature rises and cervical mucus becomes egg white-like around the same time in the subsequent cycles. Knowing this will help you determine the best time to have sex to maximize your chances of getting pregnant.

8. To increase your conception odds, try and have sex at least on alternate days during your most fertile period. 

Along with charting basal body temperature and cervical mucus, you can also use our Ovulation Calculator to determine your most fertile days.

What if charting basal body temperature and cervical mucus doesn't work for you?

If the prospect of charting your temperature daily seems stressful and time-consuming, you can try other methods to predict ovulation, such as:

• Ovulation test kit: This measures your luteinizing hormone (LH) levels to determine when you're about to start ovulating.

• Frequent sex: Having sex every other day in the two weeks in the middle of your menstrual cycle can help increase your odds of getting pregnant.

• Ovulation Calculator: Use our free and accurate Ovulation Calculator to predict your most fertile days.

When to see a Doctor

Consult your Doctor to determine if following the basal body temperature method to track ovulation is right for you. Your Doctor may recommend using a combination of natural family planning methods, such as the basal body temperature method along with the cervical mucus method. 

You can also use our Ovulation Calculator along with the basal body temperature method to determine your ovulation period.