Sarah is a freelance writer with a focus on health and wellness. She has written for publications like Women's Health, Healthline, and Parents. She taught creative writing for five years, and has a bachelor's degree in English from Southern Connecticut State University.
Michael Menna, DO, is a board-certified, active attending emergency medicine physician at White Plains Hospital in White Plains, New York.
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When it comes to family planning, sometimes the simplest tools are the best. A basal body thermometer (BBT) is one of the most convenient ways to get a good read on your fertility: because a person’s temperature fluctuates during their menstrual cycle, peaking right after ovulation and then dropping again with menstruation, a BBT can clue you into the basic rhythm and flow of your cycle. Using the data you collect from your BBT each morning (before you get out of bed), you can track your temperature changes on a chart to see at what times of the month you’re typically fertile.
The Easy@Home Smart Basal Thermometer's backlit screen and auto-sync with the Premom app makes tracking your temperature easy. The wearable Tempdrop Fertility and Ovulation Tracker takes the time commitment out of tracking your basal body temperature.
There are a few things to know, however, about buying a thermometer to detect your basal body temperature, a.k.a. your lowest, at-rest temperature. For one, you don’t technically need a one labeled as a “basal body thermometer,” specifically, but you do need one accurate enough to detect the subtle shifts in temperature that point to changes in your fertility—"you need one that can measure at least 1/10th of a degree," says says Maya Bledsoe, MD, of Austin Regional Clinic
Like many other tools, BBTs have gotten more sophisticated over the years, with many of them now linked to internet-based fertility apps that can capture and record your temperature readings for you. We spoke with OB-GYNs on how to use a BBT for the best results and evaluated them for accuracy, data storage, capabilities, your lifestyle, and more.
Here are the best basal body thermometers on the market today.
The recent Supreme Court ruling overturning Roe v. Wade and a person's Constitutional right to an abortion has created concerns around the safety and privacy of apps and technology used to track your menstrual cycle. While some of the Basal Body Thermometers we recommend do work with an app, you do not need an app in order to chart your temperature and spot the trends associated with your ovulation and menstruation dates. Apps can make predicting your fertile window easier, but you do not need one to safely and privately track your cycle.
Auto-syncing to app, if desired
Bluetooth/connectivity can be spotty
App may raise privacy concerns
It’s not often you can find a reasonably-priced product that basically offers everything you could possibly ask for, but our top pick, the smart thermometer by Easy@Home, truly does. This thermometer makes it easy to take your own fertility into your own hands (or sit back and let the BBT do all the work for you).
As far as specs, you get simple readability with the backlit LCD screen, a flexible, waterproof tip, a backup battery, and a protective, hygienic cover. The thermometer can also sync up to fertility tracking app Premom (though you don't have to use it if you're concerned about your privacy), automatically downloading your temperature readings every day and plotting them out on your fertility chart. The more data you log into the app, the easier it is for the software to predict your fertile windows for future months, helping you avoid or achieve pregnancy.
Type: Oral | Reading Time: 1.5 to 2 minutes | Battery Type: Lithium
Includes BBT and ovulation test strips
Thermometer auto-syncs to the app, if desired
Ovulation strip results don't upload to the app (for obvious reasons)
App may raise privacy concerns
Over time, a BBT can help you understand your menstrual cycle and fertility to such an extent that you may be able to feasibly conceive a pregnancy—or avoid one—using your basal body temperature and a few other physical signs of fertility, like cervical mucus. But if you don’t have time for months of trial and error with a BBT, this kit by Easy@Home gives you another layer of fertility detection: ovulation test strips.
Designed to pick up on the luteinizing hormone (LH) surge that comes with ovulation, the test strips are highly accurate at cluing you into your peak fertility window; when used in combination with the included BBT (which, FYI, is the same device we picked as our best overall BBT here), a noticeable amount of ovulation guesswork will be eliminated. In fact, once you’ve synced your BBT to the Premom app and entered in your ovulation test strip results, the app will tell you what your chances of conception are for that day.
Type: Oral | Reading Time: 1.5 to 2 minutes | Battery Type: Lithium
Reads temp automatically as you sleep
Good for women with irregular sleep schedules
Uses less accurate axillary temperature
No readable temp on device; requires app to work
App may raise privacy concerns
Most people can make temp tracking work for them, but that doesn’t always mean it’s easy. People who work or sleep irregular hours, people with other kids that keep them up at night, and or anyone who’s not keeping a regular schedule can struggle mightily with the requirements needed to keep BBT readings accurate (namely that you take your temp before you get out of bed in the morning, at roughly the same time every day).
If this sounds like you, know that you’re not alone: there are enough people out there who have this same problem that wearable BBTs have been invented, like this one from Tempdrop. It completely eliminates the need to remember anything first thing in the morning—as long as you can remember to put the BBT band around your arm before you go to sleep, you’re golden. Tempdrop monitors your basal body temperature as you sleep, inviting you to simply remove the band in the morning and sync your results to the Tempdrop app so they can be charted.
If it sounds easy, that's because it is—but there's a catch. The only thing to keep in mind, says Dr. Bledsoe, is that topical thermometers are not typically as accurate as oral ones since your skin is more responsive to environmental temperatures (e.g. if it’s warm in your room, your skin will be warm, too). We do like, though, that Tempdrop is placed with the temperature sensor in your armpit for an axillary temperature, and not just on some random spot on your body.
Type: Axillary | Reading Time: N/A | Battery Type: Lithium
No readable temp on device; requires app to work
App costs extra money to use and may raise privacy concerns
If you’re serious about tracking your temperature and plan to use it to capture a clear overall picture of your fertility, we suggest getting a BBT that’s auto-linked to an app, like the Femometer Smart Basal Thermometer. This way, you won’t even have to look at your temp in the morning, let alone plot it out on a paper chart—the BBT will capture and record your temperature for you, logging it into the Femometer app for you to check out later on.
Femometer's app works similarly to other fertility tracking apps out there: its algorithms can interpret all your data to predict your fertile window each month, plus there’s space to add any ovulation and progesterone marker (PdG) test results, too.
Type: Oral | Reading Time: 1 to 3 minutes | Battery Type: Lithium
Yellow backlit screen can be read in dark
No button; starts taking temp as soon as you open it
App costs extra money to use and may raise privacy concerns
If you’ve decided to embrace tracking your basal body temperature, you’ll have to commit to taking your temperature around the same time every day—and the best time to do that is first thing in the morning before you get up and start moving around. And depending on your sleeping arrangement and wake time, that might mean taking your temperature in a dark room. That’s why we picked the non-smart version of Femometer’s BBT: it doesn’t auto-sync to the app, but it does feature a large, backlit LCD screen to make it easy for you to read your temp in the early hours of the day or in a dark room.
We also like that it won’t blind you or your bed partner with its soft, yellow glow, so if you’re not ready to actually wake up for the day, there’s a chance you can take your temp, roll over, and go right back to sleep.
Type: Oral | Reading Time: Varies based on mode | Battery Type: Lithium
Quick-warming tip for fast results
On/off button can be hard to press down
BBTs naturally take longer to read your temperature than a regular thermometer, since they’re working to obtain your lowest at-rest reading. But trust us, there is no length of time longer than the one spent waiting for your BBT to give you a reading at the crack of dawn so you can just run to the bathroom and start your day already.
That’s why we love the digital thermometer by iProven: with readings taken in one minute or less, sometimes, it can capture an accurate BBT in a short time frame thanks to its quick-warming tip. (And its accurate is to a one hundredth of a degree.) We also appreciate that this BBT remembers your previous reading, so it’s okay if you forget to log your temperature for a day.
Type: Oral | Reading Time: 1 minute | Battery Type: Alkaline
If you want a basal body thermometer that basically does it all without getting too fancy, the Easy@Home Smart Basal Thermometer is a tiny powerhouse in a simple package. Between the backlit screen and the auto-sync capability to the Premom app, it literally couldn’t be any easier to use this device. For anyone who wants to capture their daily basal body temp but can’t commit to taking their readings at the same time every morning we suggest trying the wearable Tempdrop Fertility and Ovulation Tracker.
To find the best basal body thermometers, we asked two OBGYNs the most important things to consider before choosing the right one for you. They both agreed that accuracy was key: you can use any thermometer as a basal body thermometer, but it has to be able to capture a temperature reading at least to a tenth of a degree, if not to a hundredth. Otherwise, you won’t be able to detect the small differences in fertility-related temp changes throughout your cycle.
We researched BBTs meeting those accuracy requirements, narrowing down the many options by looking for devices offering additional convenience features, like backlit displays, quick reading capabilities, and auto-syncing app connectivity for totally effortless tracking. Whether you want to invest in a BBT that does the work for you or keep it simple, there’s a BBT on this list to meet your needs.
Whatever other features you look for, any BBT you choose has to be accurate. A thermometer that can take readings to tenth of a degree is the minimum for any basal body thermometer, per a 2017 review in Bioengineering & Translational Medicine. While you can opt for more accuracy, choosing a BBT that reads up to one hundredth of a degree, one tenth of a degree is sufficient, explains Dr. Bledsoe.
Once you know the data you’re collecting is accurate, you’ll have to figure out what to do with it. You can track it yourself, either in an app or on paper, or leave it up to the BBT (if it’s connected to an app) to auto-sync your data.
“[You may want] to use an app if you are not able to plot your temperatures on a graph, or want to see trends,” says OB-GYN Rachel Adams, MD, of Metropolitan OB-GYN in Baltimore, Maryland.
If you’re planning to track your data yourself, you may want to choose a BBT that saves a certain number of previous temperatures in case you forget to write them down a few days in a row.
In order for your temperature tracking to be accurate, says Dr. Bledsoe, you’ll need to take your temperature before you get out of bed, since moving around will increase your basal body temp pretty quickly and skew your readings. It’s also generally advised that you take your temperature around the same time each morning, since body temperatures change throughout the day. Other factors can interfere with the accuracy of your tracking, too.
“Basal body temperature can be influenced by viral illness, stress, alcohol, and sleep disturbances,” says Dr. Adams. “[It’s recommended that you get] three months of data prior to using it as a method for natural family and fertility planning.”
Most women can make a BBT work for them, though, even with an irregular sleep schedule or unexpected events. Dr. Bledsoe says you only need to be lying in bed for about one hour before using a BBT, so if you had a restless night it’s still possible to get a usable temperature reading. If you’re really concerned about the way your lifestyle might interfere with your tracking, the invention of wearable BBTs was made with people like you in mind.
BBTs read your lowest body temperature after a period of rest. You take it every morning before you get out of bed, record the reading (either by app or on paper), and then use the data collected over time to calculate the length of your menstrual cycle and estimate your ovulation timing, or fertility window. “When you ovulate, your basal body temperature will go up by 0.5 degree Fahrenheit,” says Dr. Adams, “and will stay elevated during your cycle after ovulation.”
While this can help you figure out the details of your cycle and ovulation patterns over time, BBT can’t warn you ahead of time that you’re going to ovulate or let you know when it’s happening, says Dr. Adams: “Tracking your basal body temperature only allows a person to look retrospectively and determine when they already ovulated—it does not give you real time information on when you ovulate.”
In that way, accurate use of a BBT over a longer period of time (three or four months, for example) is the only way it can help you track your fertility.
According to Dr. Bledsoe, technically any thermometer will do: “It doesn’t have to be a BBT- specific thermometer; just get one that goes to the tenth degree.” That said, many standard oral thermometers don’t go to the tenth degree, so you definitely can’t just use a regular thermometer and a BBT totally interchangeably without doing some investigating. If the thermometer you already have at home goes to the tenth degree, great—but if it doesn’t, you’ll have to look for one that does.
It’s a simple but important difference, says Dr. Adams, coming down only to the basal body thermometer’s ability to detect subtle changes in your lowest, at-rest temperature. A regular thermometer, unless it reads to the one tenth degree, can’t accurately detect your basal body temp. Pretty much every thermometer sold as a BBT will capture this degree of accuracy.
Sarah Bradley has been writing health content since 2017—everything from product roundups and illness FAQs to nutrition explainers and the dish on diet trends. She knows how important it is to receive trustworthy and expert-approved advice about over-the-counter products that manage everyday health conditions, from GI issues and allergies to chronic headaches and joint pain.
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MedlinePlus. Luteinizing hormone (LH) levels test.
Leiva R. Use of a home-based PDG urine test to confirm ovulation. ClinicalTrials.gov.
Su HW, Yi YC, Wei TY, Chang TC, Cheng CM. Detection of ovulation, a review of currently available methods. Bioeng Transl Med. 2017;2(3):238-246. doi:10.1002/btm2.10058
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