How much does basal temperature rise after ovulation?

MedlinePlus says the difference between phases is most often less than 1 degree, with a rise of about 0.2 degrees or more.

When should I take my basal body temperature?

In the morning before you get out of bed, at the same time each day if possible.

Can I use a regular thermometer?

MedlinePlus says use a basal thermometer or a digital one accurate to a tenth of a degree.

Does BBT predict ovulation?

The rise appears after ovulation, so charting over several cycles helps you see a pattern.

Is BBT tracking reliable birth control?

The CDC lists typical-use failure rates of 2% to 23% for fertility awareness-based methods.

Home / Home health monitoring

Basal body thermometer

By the Life in Good Form editors. Updated 2026-10-15.

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Quick answerA basal body thermometer reads your resting temperature to a finer level than a regular thermometer. MedlinePlus says your temperature rises after ovulation and stays higher until the end of the cycle; the difference is most often less than 1 degree, so use a basal or digital thermometer accurate to a tenth of a degree. Take it in your mouth each morning before you get out of bed, at the same time if possible, and chart it. A rise of about 0.2 degrees or more above the previous 6 days marks the shift.

Our picks at a glance

easy@Home Digital Basal Body Thermometer. Best for: Simple daily charting. See options on Amazon
Bluetooth basal body thermometer. Best for: People who prefer app charting. See options on Amazon

Compare the picks and what to watch out for

What basal body temperature shows

MedlinePlus explains that after you ovulate, your body temperature rises and stays at a higher level for the rest of the cycle, then falls again at the end. The difference between the two phases is most often less than 1 degree. Charting it over several cycles can reveal a pattern that helps you identify your most fertile days.

Because the rise appears after ovulation, a single cycle's chart shows that ovulation has likely already happened. That is why many people combine temperature with other signs, described below.

How to take your basal temperature

Right after waking. Take it in the morning before you get out of bed.
Same time daily. Try to measure at the same time every day if possible.
By mouth, fully. Keep the thermometer in your mouth for 5 minutes or until it signals it is done.
Stay still. Activity can raise body temperature slightly.
Between marks? If the reading falls between 2 marks, record the lower number.
Chart it. Write down your temperature every day.

These steps are from MedlinePlus. Keep the thermometer on your nightstand so you can reach it without getting up.

Reading your chart

What you see	What it suggests	Source
Lower temperatures early in the cycle	Before ovulation	MedlinePlus
A rise of about 0.2 degrees or more above the previous 6 days	The shift after ovulation	MedlinePlus
Temperatures stay higher	The rest of that cycle	MedlinePlus
Temperatures fall	End of the cycle	MedlinePlus

MedlinePlus says that when you look at a complete cycle, you will probably notice a point where temperatures become higher than in the first part of the cycle. Look for that overall pattern rather than reading too much into one day, and compare several cycles.

Pairing temperature with other signs

MedlinePlus describes other ways to spot fertile days. Cervical fluid changes as the body prepares to release an egg: it turns wet and creamy, then slippery, stretchy and clear like egg white near ovulation. For irregular cycles, an ovulation predictor kit that checks urine for luteinizing hormone (LH) can help, and these are sold without a prescription.

MedlinePlus also notes that sperm can live inside the body for less than 5 days and a released egg lives for less than 24 hours, and that couples trying to conceive are often advised to have sex between days 7 and 20 of the cycle. If a pregnancy test is next, see our pregnancy tests guide.

For timing, MedlinePlus notes that in a 28-day cycle ovulation usually happens around days 11 to 14, that the highest pregnancy rates have been reported when egg and sperm join within 4 to 6 hours of ovulation, and that sex every other day or every third day works as well as every day. It also says some lubricants can interfere with conception, so if you are trying to get pregnant, use only lubricants made not to interfere with fertility. For general lubricant guidance, see our personal lubricant guide.

Using BBT to avoid pregnancy

Fertility awareness-based methods, which include tracking temperature, work by not having sex on the days you are fertile. The CDC lists a range of typical-use failure rates of 2% to 23% for these methods and says failure rates vary across them. Most contraceptive methods do not protect against sexually transmitted infections. If avoiding pregnancy is important, talk with a health care provider about which method fits you.

Choosing a basal thermometer

Precision. MedlinePlus says to use a basal or digital thermometer accurate to the tenth of a degree.
No mercury. The EPA notes older glass basal thermometers held about 2.25 grams of mercury; choose a digital one.
Memory or app. A thermometer that stores the last reading, or syncs to an app, makes charting easier.
Backlight. Helpful for reading in a dark bedroom.

For fever checks, see our digital thermometer guide.

What to look for when you buy

easy@Home Digital Basal Body Thermometer

Best for: Simple daily charting

A basal thermometer meant for fertility tracking, matching MedlinePlus's advice to use one accurate to a tenth of a degree.

Watch out: Take it before getting out of bed for consistent readings.

See options on Amazon

Bluetooth basal body thermometer

Best for: People who prefer app charting

Syncing readings to an app makes the daily chart MedlinePlus recommends easier to keep.

Watch out: Check which app it uses and its privacy settings.